Specwise Mcp

io.github.hybridforgelabPublished by GitHub account hybridforgelabv0.2.3Updated Nov 6, 2026

OpenAPI and JSON Schema validation and OpenAPI breaking-change diffs for AI agents.

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Overview

AI-generated overview

Local MCP server that lets a coding agent validate OpenAPI and JSON Schema documents and diff OpenAPI versions through the paid Specwise API.

What you can do
  • Validate an OpenAPI or Swagger 2.0 document, with each error located by JSON Pointer, line and column, plus lint warnings
  • Diff two OpenAPI 3.x versions and label each change as breaking, warning, non-breaking or info, with a semver suggestion
  • Compare a spec file against a git ref, for example after editing a spec on a branch
  • Validate a JSON Schema against its meta-schema and check data against the schema
When to use it
Useful when an assistant edits or reviews API contracts and you want automated checks that a spec is valid and that a change does not break existing clients. Also handy for checking JSON Schema and sample data before shipping.
Requirements
Runs locally over stdio with uvx (Python 3.10+, installed by uv). Needs a RapidAPI key in RAPIDAPI_KEY or an api.market key in API_MARKET_KEY; HFL_MARKETPLACE picks the marketplace when both are set. Network access to the Specwise API is required.
Before you install
The Specwise API is paid with a free plan of 15 requests a month; every tool call counts as one request. Files passed by path are sent to the third-party API for that request. Documents are limited to about 900 KiB and external $refs are not fetched, so multi-file specs must be bundled first.

Installation

In SourceWeft

  1. Open Specwise Mcp in the dashboard and add it to a workspace.
  2. Enable the server for the chats that should use its tools.

Desktop only via STDIO. STDIO servers start a local process, so they need the SourceWeft desktop host.

Other MCP clients

Follow the launch instructions in the repository.

README

Specwise MCP server

[M8ven Score] [CI] [PyPI] [Python 3.10+] [License: MIT]

Let your coding agent check an API contract: validate an OpenAPI document, find the breaking changes between two versions (also against git), and validate JSON Schemas and data.

The server is open source (MIT). It calls the Specwise API, which is paid, with a free plan.

  • You use your own key, from RapidAPI or api.market.
  • Every tool call is one request on your plan.
  • The free Basic plan has 15 requests a month, with a hard limit, so it never runs up a bill.

1. Get a key

marketplace
RapidAPIplans
api.marketstore

2. Add the server to your MCP client

The server runs locally over stdio with uv. Put your key in its environment.

JSON configuration (Claude Desktop, Cursor, VS Code and most clients):

json
{  "mcpServers": {    "specwise": {      "command": "uvx",      "args": ["--from", "hybridforgelab-specwise-mcp", "specwise-mcp"],      "env": { "RAPIDAPI_KEY": "your-rapidapi-key" }    }  }}

Claude Code:

bash
claude mcp add specwise --env RAPIDAPI_KEY=your-rapidapi-key -- uvx --from hybridforgelab-specwise-mcp specwise-mcp

Environment

variablemeaning
RAPIDAPI_KEYyour RapidAPI key
API_MARKET_KEYyour api.market key, used when RAPIDAPI_KEY is not set
HFL_MARKETPLACErapidapi or apimarket, when both keys are set

Without a key the server still starts. The first tool call then explains where to get one.

Also listed on Glama:

[specwise-mcp on Glama]

3. Tools

toolwhat it does
validate_openapi(spec=… | spec_path=…)every error with its JSON Pointer, line and column, plus lint warnings (OpenAPI 3.x and Swagger 2.0)
diff_openapi(...)each change between two OpenAPI 3.x versions is breaking, warning, non-breaking or info, with a semver suggestion
validate_json_schema(schema=… | schema_path=…, instance=… | instance_path=…, draft=None)checks the schema against its meta-schema and, if given, the data against the schema

diff_openapi takes the two versions in one of three ways:

  • base and revision as text;
  • base_path and revision_path as files;
  • revision_path with base_git_ref. For example, after editing a spec: revision_path="openapi.yaml", base_git_ref="main".

Every tool returns the API's JSON response.

  • When the marketplace reports it, quota_remaining is added: the requests left on your plan this month.
  • Errors are explained in plain words, with what to do next:
    • key refused, with the link to subscribe;
    • quota reached, with the plans;
    • input the API couldn't process, with the API's reason.

Privacy

  • Local files are read only when a tool is given their path. They are sent to the API for that one request.
  • The API processes inputs in memory and doesn't store them. See the privacy policy.
  • Your key is only sent to the marketplace you chose.

Limits

  • Documents up to about 900 KiB each.
  • External $refs are not fetched. Bundle multi-file specs first (redocly bundle).
  • The diff needs OpenAPI 3.x; Swagger 2.0 can be validated, not diffed.
  • The server needs Python 3.10+ (uv installs it for you).

Development

bash
uv venv && uv pip install -e ".[dev]".venv/bin/pytest            # unit tests, no network; 100% coverage required.venv/bin/ruff check src tests scripts

scripts/e2e_stdio.py specwise runs the server over stdio, as a client would, and calls its tools against the real API. It needs RAPIDAPI_KEY or API_MARKET_KEY.

Licence

MIT. Specwise itself is a paid API with a free plan, run by Hybrid Forge Lab.

Source: README.md at commit 92d4ae7

Tools

0
SourceWeft started this package once in an isolated sandbox, without credentials, to list its tools. That failed: the package type cannot run in the sandbox.

Version history

3
  1. v0.2.3LatestNov 6, 2026
  2. v0.2.2Nov 3, 2026
  3. v0.2.0Nov 3, 2026

Score

50% of the applicable checks met

How complete this listing is, computed from the registry entry, the endpoint and public sources. Not a rating of the server and not a statement that it is safe or working today: reachability is a dated check, and no installs or reviews go into the score.

  • Reached in the last 30 days25 pts

    Keep the endpoint answering the MCP handshake; SourceWeft probes it every 30 days.

  • Auth declared10 pts

    Declare the credential headers in the registry entry, or keep the endpoint answering the probe so its auth can be classified.

  • Tools listed15 pts

    Answer tools/list without a credential, or ship a package that starts in a sandbox without one.

  • DescriptionRequired15 pts
  • Logo10 pts
  • Documentation15 pts
  • License10 pts