ModelSpec

ModelSpec remote MCP server

Read-only MCP tools over the ModelSpec catalogue. Data tools require an API key. The site stays on Cloudflare Pages; this Worker only answers https://api.modelspec.dev/mcp and its public server card at https://api.modelspec.dev/.well-known/mcp/server-card.json.

Official registry listing

The root server.json describes the keyed remote server using the official registry's 2025-12-11 schema. Its checked-in version records the deployment observed when the listing was added. The schema is vendored unchanged in tests/fixtures/mcp_registry/ so validation runs offline.

After review, merge, and a successful MCP deployment, an operator can dispatch Publish MCP registry listing on main. It verifies that the live Worker's serverInfo.version matches the selected commit and writes that version to a temporary manifest. A deployment mismatch fails before authentication or publication. The workflow uses checksum-pinned mcp-publisher v1.8.1 and GitHub OIDC. It has no push trigger and needs no registry secret.

Registry metadata declares a required, secret Authorization: Bearer key. Keys come from pricing and keys.

Sources: registry schema, official publishing workflow, and publisher v1.8.1.

Smithery listing

After review, merge, and a successful MCP deployment, publish the remote URL with the required API-key configuration below. Replace YOUR_SMITHERY_NAMESPACE with the namespace owned by the publishing account:

smithery mcp publish "https://api.modelspec.dev/mcp" \

-n @YOUR_SMITHERY_NAMESPACE/modelspec \ --config-schema '{"type":"object","properties":{"apiKey":{"type":"string","title":"ModelSpec API key","description":"Create one at https://modelspec.dev/pricing/","x-from":{"header":"x-api-key"},"x-to":{"header":"x-api-key"}}},"required":["apiKey"]}'

Smithery collects each user's ModelSpec key and forwards it as the raw x-api-key header value. The MCP Worker converts it to Authorization: Bearer for API calls. This alias applies only to MCP; direct /v1/* API calls still accept only Bearer authentication.

The public server card requires no key. Its serverInfo matches initialize, including the deployed commit as its version. It declares authentication: {"required": true, "schemes": ["bearer"]} and generates its tools from the same registrations as tools/list. The card uses Cache-Control: public, max-age=300.

Sources: Smithery publishing and configuration transport.

SDK and transport

McpAgent is deprecated and feature-frozen; it exists for sessionful servers that need Durable Object state. These tools are proxies: each call hits the public rank API, policy-check API, or the static JSON export and returns that body plus the origin URL. There is nothing to persist.

Read (2026-09-18):

• https://developers.cloudflare.com/agents/model-context-protocol/apis/handler-api/
• https://developers.cloudflare.com/agents/model-context-protocol/guides/remote-mcp-server/
• https://developers.cloudflare.com/agents/model-context-protocol/apis/agent-api/

Route

Workers routes api.modelspec.dev/mcp* and api.modelspec.dev/.well-known/mcp/server-card.json on zone modelspec.dev belong to this Worker. The rank Worker already owns api.modelspec.dev/*; the more specific patterns win. The card route is exact, so discovery clients must use its URL without a query string. Other API routes keep their existing Worker. The CI token can edit Workers routes and cannot create DNS, so there is no new hostname.

Tools

Successful calls pass through the origin. Null on a card means not researched.

rank, policy_check, decide, compare_models, and hardware_fit use the RANK service binding because a same-zone Worker fetch to the public API hostname reaches the zone origin and returns 522. All five forward the key as Authorization: Bearer . The API validates presented keys and returns its auth/payment errors unchanged.

MCP accepts either Authorization: Bearer or x-api-key: . If both headers are present, their keys must agree; conflicting credentials return HTTP 400 with a JSON-RPC error. Keys never appear in logs or error messages.

All data tools require a ModelSpec key, including when MCP_REQUIRE_API_KEY="false". Missing or malformed credentials return a 401 missing_api_key refusal before any origin call. This includes rank, policy_check, decide, compare_models, hardware_fit, vocab, model_info and list_use_cases. initialize and tools/list remain public. Feedback stays keyless and carries no model data. Use an existing key, or see pricing for availability.

decide accepts the decision spec defined by docs/decision-contract.md. Its MCP input schema comes from the generated docs/decision-contract.schema.json, so the API and MCP contracts cannot drift. Read vocab first for valid facet ids. Use where for Musts that exclude and optimize.weights for Prefers that rank without excluding. Unknown capability values appear in may_qualify. Pin snapshot to reproduce a decision.

compare_models accepts only {models: ["lab/a", "lab/b"]}, with 2 to 4 distinct catalogue ids. It returns the current snapshot's sourced facts, offerings and evidence in caller order. It does not rank or choose a winner. Unknown values stay null, and omitted counts removed records. The entire MCP text stays within 16 KB. An oversized origin response becomes a compact response_too_large tool error and returns no comparison data. This named model comparison does not change the snapshot comparison at /v1/compare.

hardware_fit accepts model, sku, device_count, memory, runtime, quantisation, batch and context. Memory is an optional override in decimal GB per device. Omitted or null inputs reach the API and return undetermined when they prevent assessment. Unknown SKU or quantisation identifiers also reach the API. The tool preserves the endpoint's complete answer and citations. A measured answer cites the exact run. An estimated answer gives estimated_fit: likely|unlikely, a memory margin, the formula, inputs and assumptions. An estimate never proves fit or contains fits: true.

Client config

Run modelspec setup mcp --client claude-code or modelspec setup mcp --client claude-desktop for the client's native snippet. Claude Code:

{

"mcpServers": { "modelspec": { "type": "http", "url": "https://api.modelspec.dev/mcp", "headers": { "Authorization": "Bearer " } } } }

Claude Desktop uses the mcp-remote stdio bridge and requires Node.js/npx:

{

"mcpServers": { "modelspec": { "command": "npx", "args": ["-y", "mcp-remote", "https://api.modelspec.dev/mcp", "--header", "Authorization:${MODELSPEC_AUTH_HEADER}"], "env": {"MODELSPEC_AUTH_HEADER": "Bearer "} } } }

macOS GUI apps do not inherit your shell environment. Explicitly replace the placeholder in the env block with your key, retaining Bearer ; that stores the key in this config. The CLI's setup command writes the placeholder and never copies a saved or environment key into the config. The env block and header form follow the mcp-remote documentation.

Local

npm install

npm test npm run typecheck npx wrangler@4.134.0 dev --local --var BUILD_COMMIT:dev

Deploy is .github/workflows/mcp.yml on push to main only. Do not deploy from a laptop.