API platform engineers and developer-tooling teams use this prompt when a model-generated OpenAPI specification is truncated mid-stream. The most common causes are hitting the model's max_tokens limit, a streaming connection interruption, or an early stop signal. This prompt recovers the partial specification by repairing truncated paths, schema objects, and components blocks into a syntactically valid OpenAPI document that passes standard validator checks. It is designed for post-generation repair loops, not for initial schema authoring.
Prompt
Truncated OpenAPI Schema Recovery Prompt Template

When to Use This Prompt
Recover a truncated OpenAPI specification into a valid, parseable document ready for downstream tooling.
The prompt assumes you have a partial, well-formed OpenAPI JSON or YAML fragment that was cut off before completion. It instructs the model to close all open structures, infer reasonable defaults for missing required fields, and flag any endpoints or schemas that could not be fully recovered. The output is a complete, parseable OpenAPI document ready for downstream validation, mocking, or code generation. This is a recovery tool, not a design tool—do not use it to author a spec from scratch or to add new endpoints that were never present in the partial input.
Before using this prompt, confirm that the truncation is structural rather than semantic. If the model stopped because it ran out of context or misunderstood the task, a simple continuation may repeat the error. This prompt works best when the partial output is already well-formed up to the truncation point. If the fragment contains syntax errors before the cutoff, run a basic structural repair first. After recovery, always validate the output with an OpenAPI linter and review any flagged endpoints before generating client SDKs or publishing the spec.
Use Case Fit
Where the Truncated OpenAPI Schema Recovery Prompt works, where it fails, and what you must provide before using it in production.
Good Fit: Partial Spec with Intact Structure
Use when: The model output contains a valid OpenAPI header, paths, or components block that was cut off mid-object. The structural skeleton is present, and the prompt only needs to close braces, complete the last endpoint, and infer missing schema references. Guardrail: Validate the input has at least one complete path item before attempting repair; otherwise, escalate to regeneration.
Bad Fit: Hallucinated or Fabricated Endpoints
Avoid when: The partial spec contains endpoints, parameters, or schemas the model invented rather than derived from source documentation. Repairing hallucinated content produces a valid spec that misrepresents the actual API. Guardrail: Run a source-grounding check against the original API docs before repair. If endpoints don't match known routes, discard and regenerate with stricter grounding instructions.
Required Input: Truncation Boundary Metadata
Risk: Without knowing where the output was cut, the repair prompt may duplicate content, miss the breakpoint, or corrupt the last valid object. Guardrail: Always pass the finish_reason (must be length or content_filter) and the exact last 200 characters of the partial output as context. This lets the model identify the breakpoint and resume cleanly without guessing.
Operational Risk: Silent Schema Corruption
Risk: A repaired spec may pass an OpenAPI validator but contain subtly wrong field types, missing required parameters, or broken $ref pointers that downstream code generators won't catch until runtime. Guardrail: Add a post-repair $ref resolution check and a required-field completeness scan. Flag any spec where required arrays reference fields not present in the sibling properties block.
Operational Risk: Token-Limit Cascade
Risk: The repair prompt itself consumes tokens. If the partial spec is near the model's context limit, the repair request may also truncate, creating a recursive failure loop. Guardrail: Measure the partial spec's token count before repair. If it exceeds 80% of the model's context window, split the repair into two passes: structural closure first, then schema completion. Never attempt repair if the partial input exceeds 95% of the context limit.
Bad Fit: Multi-File or Split Specs
Avoid when: The partial output is one fragment of a multi-file OpenAPI spec where $ref pointers cross file boundaries. The repair prompt cannot resolve external references and will produce a spec with dangling pointers. Guardrail: Detect external $ref values (those starting with ./ or URLs) in the partial input. If present, bundle the referenced files into a single document before repair, or escalate to a multi-file assembly workflow.
Copy-Ready Prompt Template
A production-ready prompt for recovering truncated OpenAPI specifications into valid, parseable documents.
This prompt template is designed to be pasted directly into your repair harness when an OpenAPI specification generation has been cut off by token limits, streaming interruptions, or model early-stopping. It instructs the model to analyze the partial specification, identify structural breaks, and produce a complete, valid OpenAPI document. The template uses square-bracket placeholders that you must replace with actual values before sending to the model. Treat this as a recovery tool, not a primary generation path—always prefer preventing truncation through token budgeting and streaming controls first.
textYou are an API specification repair assistant. Your task is to recover a truncated OpenAPI specification into a complete, valid document. ## INPUT Partial OpenAPI specification (may be truncated mid-object, mid-array, or mid-string): [PARTIAL_SPEC] ## TASK 1. Parse the partial specification and identify the exact truncation point. 2. Determine which structural elements are incomplete: paths, schema components, parameters, responses, security definitions, or tags. 3. For each incomplete element, infer the intended structure from context, naming conventions, and partial field values. 4. Complete the specification by: - Closing all unclosed objects, arrays, and strings. - Adding missing required OpenAPI fields (openapi, info, paths) if absent. - Preserving all valid partial content without modification. - Marking unrecoverable elements with `x-repaired: true` and `x-repair-note` descriptions. 5. Output ONLY the complete, valid OpenAPI specification in JSON or YAML format matching the input format. ## CONSTRAINTS - Do not invent endpoints, schemas, or parameters beyond what the partial input strongly implies. - Preserve all existing field names, descriptions, and examples exactly as they appear. - If a path or schema is too incomplete to infer, include it as a stub with `x-repair-status: "incomplete"`. - Maintain the original OpenAPI version (2.0, 3.0, 3.1) detected from the input. - Do not add explanatory text outside the specification output. ## OUTPUT FORMAT Valid [OUTPUT_FORMAT] matching the input specification format. ## EXAMPLES [REPAIR_EXAMPLES]
Adaptation guidance: Replace [PARTIAL_SPEC] with the raw truncated OpenAPI content. Set [OUTPUT_FORMAT] to JSON or YAML based on your pipeline requirements. The [REPAIR_EXAMPLES] placeholder should contain 1-2 examples of truncated-to-repaired specification pairs showing the expected recovery behavior—include at least one example with a mid-object truncation and one with a missing closing tag. For high-stakes API gateways, add a [RISK_LEVEL] constraint that gates unrecoverable elements for human review before deployment. Wire the output through an OpenAPI validator (such as swagger-parser or openapi-validator) before accepting the repair. If the validator fails, feed the error message back into a retry loop with this same prompt, appending the validation errors to [CONSTRAINTS].
Prompt Variables
Inputs the Truncated OpenAPI Schema Recovery prompt needs to produce a valid, complete specification. Each placeholder must be populated before the prompt is sent. Validation notes describe how to confirm the input is well-formed.
| Placeholder | Purpose | Example | Validation Notes |
|---|---|---|---|
[TRUNCATED_OPENAPI_DOCUMENT] | The partial OpenAPI specification text that was cut off during generation. This is the primary input to repair. | {"openapi": "3.0.3", "info": {...}, "paths": {"/users": {"get": {"summary": "List users", "responses": {"200": {"description": "A list of users", "content": {"application/json": {"schema": {"type": "array", "items": {"$ref": "#/components/schemas/ | Parse check: input must be a non-empty string. Content check: input should contain recognizable OpenAPI keywords (openapi, paths, components, info). Truncation check: input should end mid-token, mid-string, or with unclosed braces/brackets. |
[OPENAPI_VERSION] | The target OpenAPI specification version for the repaired document. Ensures the recovery prompt uses version-appropriate syntax and rules. | 3.0.3 | Enum check: value must be a valid OpenAPI version string (3.0.x, 3.1.x). Schema check: version must match the version declared in the truncated document if present. |
[REQUIRED_ENDPOINT_LIST] | A list of endpoint paths and HTTP methods that must be present and complete in the repaired specification. Prevents the model from omitting critical API surfaces. | ["/users:get", "/users:post", "/users/{id}:get", "/users/{id}:patch"] | Schema check: must be a JSON array of strings. Format check: each string must follow the pattern '/path:method'. Completeness check: list should cover all endpoints expected in the final spec. |
[COMPONENT_SCHEMA_NAMES] | The expected set of component schema names that should be defined under #/components/schemas/. Guides the model to recover schemas that were partially defined or referenced but not completed. | ["User", "UserCreateRequest", "UserUpdateRequest", "ErrorResponse", "PaginationMeta"] | Schema check: must be a JSON array of non-empty strings. Reference check: names should match $ref values found in the truncated document. Null allowed: true if no schemas are expected. |
[SECURITY_SCHEME_TYPE] | The authentication method used by the API. Informs how the model repairs securityDefinitions or securitySchemes blocks if they were truncated. | bearerAuth | Enum check: value should be a known security scheme type (bearerAuth, apiKey, oauth2, openIdConnect, basicAuth). Null allowed: true if the API has no security requirements. |
[CONTEXT_HINT] | Optional natural language description of the API's purpose, domain, or business logic. Helps the model infer correct field names, data types, and endpoint behavior when the truncated text is ambiguous. | A REST API for a SaaS user management system. Users have profiles, roles, and team memberships. Endpoints support CRUD operations, pagination, and filtering by status. | Type check: must be a string or null. Length check: if provided, should be under 500 tokens to avoid diluting the primary repair task. Null allowed: true. |
[OUTPUT_SCHEMA] | The expected structure of the model's response. Instructs the model to return the repaired OpenAPI document and a repair summary in a structured format for downstream parsing. | {"repaired_spec": "string", "repair_summary": {"endpoints_recovered": ["string"], "schemas_recovered": ["string"], "unrecoverable_sections": ["string"], "repair_notes": "string"}} | Schema check: must be a valid JSON Schema or TypeScript interface definition. Field check: must include a field for the repaired spec string and a structured repair summary. Parse check: output schema must be parseable by the application harness. |
Implementation Harness Notes
How to wire the Truncated OpenAPI Schema Recovery prompt into an application repair pipeline with validation, retries, and observability.
This prompt is designed to be called after a primary generation step fails OpenAPI validation or is truncated by token limits. It should not be the first attempt at schema generation. The harness must receive the partial OpenAPI document, the original generation context, and the specific truncation point or validation errors before invoking this recovery prompt. Treat this as a repair step in a pipeline, not a standalone generator.
Wire the prompt into a repair loop with a hard retry limit of 2–3 attempts. After each recovery attempt, run the output through an OpenAPI validator (such as @apidevtools/swagger-parser or openapi-schema-validator) and a structural completeness check that verifies required OpenAPI fields (openapi, info, paths) are present and non-empty. If validation fails, feed the specific validator error messages back into the [VALIDATION_ERRORS] placeholder on the next retry. Log every attempt—including the partial input, recovery output, validator result, and error details—to a structured trace for debugging.
For production use, prefer models with strong JSON and code generation capabilities (such as gpt-4o, claude-3-5-sonnet, or equivalent). Set response_format to { "type": "json_object" } when the provider supports it, but do not rely on structured output mode alone—always validate the result. If the recovery prompt fails after the retry budget, escalate to a human review queue with the partial spec, all repair attempts, and validator output attached. Never silently accept an unrepaired spec into a downstream API gateway or documentation pipeline.
Expected Output Contract
Fields, format, and validation rules for the repaired OpenAPI specification. Use this contract to validate the model's output before accepting it into your API pipeline.
| Field or Element | Type or Format | Required | Validation Rule |
|---|---|---|---|
openapi | string (semver) | Must equal '3.0.3' or '3.1.0'. Parse as semver and reject if missing or invalid. | |
info.title | string | Non-empty string. Must match [ORIGINAL_TITLE] if provided in context. Reject if null or whitespace-only. | |
info.version | string | Non-empty string. Preserve [ORIGINAL_VERSION] if present in partial input. Reject if missing. | |
paths | object | Must be a valid JSON object with at least one path key. Each path item must contain at least one HTTP method operation. Validate with OpenAPI schema. | |
paths...responses | object | Every operation must have a responses object with at least one HTTP status code key. Reject operations with empty responses. | |
components.schemas | object | If present, each schema must have a 'type' property or '$ref'. Validate schema references resolve within the document. Null allowed if no schemas. | |
[RECOVERED_FIELD] | per schema | Any field present in [PARTIAL_SPEC] must appear in output with preserved values. No hallucinated fields beyond repair scope. Diff against partial input. | |
_repair_metadata | object | Must include 'repaired_sections' (array of strings), 'unrecoverable_sections' (array of strings), and 'confidence' (string enum: 'high'|'medium'|'low'). Required for audit trail. |
Common Failure Modes
Truncated OpenAPI schemas fail in predictable ways. These are the most common breakages and how to guard against them before the repaired spec reaches your gateway or docs pipeline.
Unclosed Brace Cascade
What to watch: The model output cuts off mid-object, leaving dangling braces and unclosed nested structures. A single missing } can invalidate the entire spec. Guardrail: Run a structural JSON/YAML validator before any semantic checks. Use a brace-pairing heuristic to estimate closure depth and reject outputs with depth mismatch > 0.
Phantom Endpoint Hallucination
What to watch: The recovery prompt invents path items, parameters, or response codes that were never in the partial input. This is common when the model tries to 'complete' an API it partially recognizes. Guardrail: Diff the repaired spec against the original truncated input. Flag any new path keys, operation IDs, or schema properties that don't appear in the prefix.
Schema Component Orphan
What to watch: A $ref points to a component that was truncated and never recovered, or the recovery prompt creates a stub component with no properties. Guardrail: Resolve all $ref pointers after repair. Any reference that resolves to an empty object or missing component must be flagged for human review or re-prompting with the specific missing schema name.
Response Body Mismatch
What to watch: The repaired response schema doesn't match the operation's declared success code. The model might attach a 200 response schema to a 201 operation, or mix up array and object wrappers. Guardrail: Validate that every operation with a success response has a corresponding application/json schema. Check that the schema type matches the operation's documented return type if available in the partial input.
Parameter Duplication Across Paths
What to watch: The recovery prompt duplicates path-level parameters into the operation level, or copies query parameters across endpoints that shouldn't share them. Guardrail: Normalize parameters after repair. Merge path-item and operation parameters, then deduplicate by name + in. Flag any parameter that appears with conflicting required values.
Enum Value Truncation
What to watch: An enum array was cut off mid-value, and the recovery prompt either closes the array prematurely or invents plausible but incorrect enum members. Guardrail: Compare enum cardinality against any partial context. If the original input shows 5 of N enum values, the repaired spec should not claim exactly 5 unless the model explicitly marks the list as potentially incomplete. Add an x-repair-status: partial extension field to uncertain enums.
Evaluation Rubric
Use this rubric to test the quality of repaired OpenAPI schemas before shipping the prompt into production. Each criterion targets a specific failure mode common in truncated schema recovery.
| Criterion | Pass Standard | Failure Signal | Test Method |
|---|---|---|---|
OpenAPI Parse Validity | Output passes a standard OpenAPI 3.x parser without errors | Parser throws syntax errors, missing required fields, or invalid references | Run output through an OpenAPI validator library (e.g., swagger-parser, openapi-core) and assert zero errors |
Endpoint Completeness | All paths and HTTP methods present in [PARTIAL_SCHEMA] appear in the repaired output | Paths or methods from the partial input are missing or altered in the final output | Extract path+method tuples from [PARTIAL_SCHEMA] and diff against repaired output; assert 100% match |
Schema Reference Integrity | All $ref pointers resolve to components defined within the output or are preserved as-is from the partial input | Dangling $ref values that point to nonexistent component keys | Resolve all $ref pointers programmatically; assert no unresolved references in the final output |
No Hallucinated Endpoints | Output contains zero paths, methods, or operations not present in [PARTIAL_SCHEMA] or clearly implied by its structure | New endpoints, parameters, or response codes appear that were not in the partial input | Diff path+method+operationId sets between [PARTIAL_SCHEMA] and output; flag any additions for human review |
Component Schema Preservation | All schema objects in #/components/schemas from [PARTIAL_SCHEMA] are preserved with their original property names and types | Properties renamed, types changed, or required fields dropped from existing component schemas | Deep-compare each schema object from [PARTIAL_SCHEMA] against the repaired output; assert structural equality for all pre-existing keys |
Truncation Boundary Repair | The specific object, array, or string that was cut off at the truncation point is syntactically closed and semantically coherent | The repaired boundary introduces contradictory types, impossible values, or broken nesting | Identify the truncation point from [PARTIAL_SCHEMA]; manually inspect the repaired boundary for syntactic closure and semantic plausibility |
Response Schema Completeness | All response schemas referenced by operations include at minimum a description and a content/mediaType entry if implied by context | Response objects are empty, missing required fields, or contain placeholder-only content | Traverse all operation responses in output; assert each has a non-empty description or content block unless explicitly optional in the spec |
Info and Server Block Integrity | The info.title, info.version, and servers array from [PARTIAL_SCHEMA] are preserved exactly or completed with minimal, plausible defaults | Title or version fields are replaced with generic placeholders like 'API' or '1.0.0' without evidence from the partial input | Compare info and servers blocks from [PARTIAL_SCHEMA] against output; flag any value changes for human approval |
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Adapt This Prompt
How to adapt
Wrap the prompt in a retry harness with OpenAPI schema validation. On validation failure, feed the validator error back to the model for self-correction. Log all recovery attempts and final pass/fail status.
code[RECOVERY_PROMPT] [TRUNCATED_SPEC] [VALIDATOR_ERRORS] // injected on retry Return valid OpenAPI 3.x JSON. Fix all validator errors.
Watch for
- Silent format drift across retries where the model changes working portions
- Validator error loops where the model cannot converge
- Missing human review gate for specs that fail after N retries

About the author
Prasad Kumkar
CEO & MD, Inference Systems
Prasad Kumkar is the CEO & MD of Inference Systems and writes about AI systems architecture, LLM infrastructure, model serving, evaluation, and production deployment. Over 5+ years, he has worked across computer vision models, L5 autonomous vehicle systems, and LLM research, with a focus on taking complex AI ideas into real-world engineering systems.
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