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mcpg-plugin-transform-json-schema MCP server · F · ToolBench

mcpg-plugin-transform-json-schema

github.com/mcpg-dev/mcpg-plugin-transform-json-schema

JSON Schema validation transform plugin for mcpg. Validates a JSON value against an operator-supplied inline JSON Schema; a valid value passes through unchanged, an invalid value yields a precise transform error listing the failing instance paths. Usable as a global pre/post-dispatch transform and as a pipeline `plugin_transform` step; an optional JSON Pointer validates a sub-field. Pure compute, fully offline (no remote $ref fetch); the gateway core never depends on it.

2026-07-28+1 tools

47/100

Definition Quality50

Protocol Readiness40

Supportability45

Spec posture

Inferred effective spec 2026-07-28+·current baseline 2026-07-28

Static source inference · medium confidence · evidence: stateless requests

Current-spec patterns detected

Summary

Single tool with complete input schema and reasonable description. Schema is well-structured with proper types, enums, and defaults. However, description is terse (145 chars, below the 194-char baseline), lacks WHEN/WHY guidance, and omits error recovery hints. Parameter descriptions are present but minimal. Output schema is not documented, LLMs cannot predict the structure of TransformResult::Error messages or understand what 'Unchanged' means in context. No guidance on idempotency, side effects, or composition with other tools.

Tools (1)

json-schema-transformread only50/100

Validates a JSON value against an inline JSON Schema. A valid value passes through unchanged; an invalid value yields a TransformResult::Error listing the failing instance paths bounded by max_errors.

Issues (5)

HIGHtool ↗

Output schema not documented. LLMs cannot predict TransformResult structure (Unchanged vs Error vs Modified). Requires explicit documentation of return type and field meanings.

json-schema-transform

HIGHtool-description ↗

Tool description lacks WHEN/WHY context. 145 chars is below 194-char baseline. Does not explain when to use this vs other validation approaches, prerequisites, or error recovery paths.

json-schema-transform

MEDIUMtool-description ↗

Parameter 'pointer' description is vague ('JSON Pointer (RFC 6901) to the sub-value'). Does not explain what happens if pointer is invalid, whether empty string means root, or how to construct pointers for nested objects.

json-schema-transform

MEDIUMrecovery-guide ↗

No error handling guidance. Error messages are raw (e.g., 'pointer not found in value'). LLMs cannot determine if error is retryable, user-fixable, or fatal. No recovery suggestions.

json-schema-transform

Recommendations

Expand tool description to 150 - 250 chars. Add: 'Validates JSON against a schema. Use this to enforce data contracts before processing. Returns Unchanged if valid, Error with failing paths if invalid. Fully offline, no remote $ref fetch.'
Document output schema explicitly: 'Returns TransformResult::Unchanged (value is valid) or TransformResult::Error with a message listing failing instance paths (bounded by max_errors).'
Enhance 'pointer' parameter description: 'JSON Pointer (RFC 6901) to the sub-value to validate. Empty string or omitted = validate entire value. Example: "/user/email" validates the email field. Returns error if pointer does not exist in value.'
Add error recovery guidance in tool description: 'If validation fails, the error message lists the failing paths and constraints. Use this to guide the user on what to fix. If pointer is invalid, check the JSON structure first.'
Add idempotency note: 'This tool is read-only and idempotent, safe to call multiple times with the same input.'

Score history

Overall score trend

First recorded score · v2 rubric

47/100

Scored	Grade	Overall	Spec posture	Rubric
2026-09-23	F	47	2026-07-28+	v2