Generate MCP Server

generate-mcp-server

Generate a Model Context Protocol (MCP) server from an OpenAPI spec using Speakeasy. The MCP server exposes API operations as tools that AI assistants like Claude can call directly.

When to Use

• User wants to create an MCP server from their API
• User asks about Model Context Protocol integration
• User wants AI assistants to interact with their API
• User says: "generate MCP server", "create MCP server", "speakeasy MCP"
• User asks: "How do I make my API available to Claude?"
• User mentions: "mcp-typescript", "AI assistant tools", "Claude tools"

Inputs

Outputs

Prerequisites

1. Speakeasy CLI installed and authenticated:

speakeasy auth login
# Or for CI/AI agents:
export SPEAKEASY_API_KEY="<your-api-key>"

2. Node.js 20+ installed (for the generated MCP server).

3. A valid OpenAPI spec (3.0 or 3.1). Validate first:

speakeasy lint openapi --non-interactive -s ./openapi.yaml

Run speakeasy auth login to authenticate interactively, or set the SPEAKEASY_API_KEY environment variable.

Command

The generation uses speakeasy run after configuring the workflow, overlays, and gen.yaml. There is no single command -- follow the step-by-step workflow below.

# After all config files are in place:
speakeasy run

Step-by-Step Workflow

Step 1: Create the Scopes Overlay

Create mcp-scopes-overlay.yaml in the project root. This controls which API operations become MCP tools and what scopes they require:

# mcp-scopes-overlay.yaml
openapi: 3.1.0
overlay: 1.0.0
info:
  title: Add MCP scopes
  version: 0.0.0
actions:
  # Enable read operations
  - target: $.paths.*["get","head"]
    update:
      x-speakeasy-mcp:
        scopes: [read]
        disabled: false

  # Enable write operations
  - target: $.paths.*["post","put","delete","patch"]
    update:
      x-speakeasy-mcp:
        scopes: [write]
        disabled: false

  # Disable specific sensitive endpoints (customize as needed)
  # - target: $.paths["/admin/danger-zone"]["delete"]
  #   update:
  #     x-speakeasy-mcp:
  #       disabled: true

Step 2: Create the Workflow Configuration

Create .speakeasy/workflow.yaml:

# .speakeasy/workflow.yaml
workflowVersion: 1.0.0
speakeasyVersion: latest
sources:
  My-API:
    inputs:
      - location: ./openapi.yaml
    overlays:
      - location: mcp-scopes-overlay.yaml
    output: openapi.yaml
targets:
  mcp-server:
    target: mcp-typescript
    source: My-API

Replace ./openapi.yaml with the actual spec path or URL.

Important: Use the standalone mcp-typescript target, not typescript with enableMCPServer: true. The embedded approach (enableMCPServer flag) is deprecated.

Step 3: Configure gen.yaml

Create .speakeasy/gen.yaml:

# .speakeasy/gen.yaml
configVersion: 2.0.0
generation:
  sdkClassName: MyApiMcp
  maintainOpenAPIOrder: true
  devContainers:
    enabled: true
    schemaPath: ./openapi.yaml
typescript:
  version: 1.0.0
  packageName: my-api-mcp
  envVarPrefix: MYAPI

Key settings:

• target: mcp-typescript in workflow.yaml -- this is what triggers MCP server generation
• packageName -- the npm package name users will npx
• envVarPrefix -- prefix for auto-generated env var names

Step 4: Generate

speakeasy run

For AI-friendly output:

speakeasy run --output console 2>&1 | tail -50

Using the Generated MCP Server

CLI Usage

# Start with stdio transport (default, for local AI assistants)
npx my-api-mcp mcp start --bearer-auth "YOUR_TOKEN"

# Start with SSE transport (for networked deployment)
npx my-api-mcp mcp start --transport sse --port 3000 --bearer-auth "YOUR_TOKEN"

# Filter by scope (only expose read operations)
npx my-api-mcp mcp start --scope read --bearer-auth "YOUR_TOKEN"

# Mount specific tools only
npx my-api-mcp mcp start --tool users-get-users --tool users-create-user --bearer-auth "YOUR_TOKEN"

CLI Options

Claude Desktop Configuration

Add to claude_desktop_config.json:

{
  "mcpServers": {
    "my-api": {
      "command": "npx",
      "args": [
        "-y", "--package", "my-api-mcp",
        "--",
        "mcp", "start",
        "--bearer-auth", "<API_TOKEN>"
      ]
    }
  }
}

Claude Code Configuration

Add to .claude/settings.json or use claude mcp add:

{
  "mcpServers": {
    "my-api": {
      "command": "npx",
      "args": [
        "-y", "--package", "my-api-mcp",
        "--",
        "mcp", "start",
        "--bearer-auth", "<API_TOKEN>"
      ]
    }
  }
}

Docker Deployment

For production, use SSE transport with Docker:

# Build and run
docker-compose up -d

# Configure MCP client to use SSE endpoint
# "url": "http://localhost:32000/sse"

The generated project includes a Dockerfile and docker-compose.yaml.

Example

Full example generating an MCP server for a pet store API:

# 1. Validate the spec
speakeasy lint openapi --non-interactive -s ./petstore.yaml

# 2. Create scopes overlay
cat > mcp-scopes-overlay.yaml << 'EOF'
openapi: 3.1.0
overlay: 1.0.0
info:
  title: Add MCP scopes
  version: 0.0.0
actions:
  - target: $.paths.*["get","head"]
    update:
      x-speakeasy-mcp:
        scopes: [read]
        disabled: false
  - target: $.paths.*["post","put","delete","patch"]
    update:
      x-speakeasy-mcp:
        scopes: [write]
        disabled: false
EOF

# 3. Create workflow (assumes .speakeasy/ dir exists)
mkdir -p .speakeasy
cat > .speakeasy/workflow.yaml << 'EOF'
workflowVersion: 1.0.0
speakeasyVersion: latest
sources:
  petstore:
    inputs:
      - location: ./petstore.yaml
    overlays:
      - location: mcp-scopes-overlay.yaml
    output: openapi.yaml
targets:
  mcp-server:
    target: mcp-typescript
    source: petstore
EOF

# 4. Create gen.yaml
cat > .speakeasy/gen.yaml << 'EOF'
configVersion: 2.0.0
generation:
  sdkClassName: PetStoreMcp
  maintainOpenAPIOrder: true
typescript:
  version: 1.0.0
  packageName: petstore-mcp
  envVarPrefix: PETSTORE
EOF

# 5. Generate
speakeasy run

# 6. Test locally
npx petstore-mcp mcp start --bearer-auth "test-token"

Expected Output

Workflow completed successfully.
Generated TypeScript MCP server in ./

The generated project contains:

• src/mcp-server/server.ts -- Main MCP server factory
• src/mcp-server/tools/ -- One tool per API operation
• src/mcp-server/mcp-server.ts -- CLI entry point
• src/mcp-server/scopes.ts -- Scope definitions

Best Practices

1. Use overlays for MCP config -- never edit the source OpenAPI spec directly
2. Enhance descriptions for AI -- add documentation overlays so AI assistants understand tool purpose
3. Filter tools at runtime -- use --scope and --tool flags to limit what is exposed
4. Use environment variables -- never hardcode tokens in config files
5. Start with read-only scopes -- add write scopes only when needed
6. Create a dedicated MCP package -- keep MCP separate from your main SDK

What NOT to Do

• Do NOT modify the source OpenAPI spec to add x-speakeasy-mcp -- use overlays instead
• Do NOT hardcode API tokens in Claude Desktop or Claude Code config files -- use environment variables or secrets managers
• Do NOT expose all operations without reviewing them -- disable sensitive admin endpoints
• Do NOT skip spec validation -- invalid specs produce broken MCP servers
• Do NOT use the deprecated enableMCPServer: true flag in gen.yaml -- use the standalone mcp-typescript target in workflow.yaml instead
• Do NOT generate without a scopes overlay -- tools will lack scope definitions
• Do NOT use the generated MCP server as a general SDK -- it is purpose-built for AI assistant integration

Troubleshooting

MCP server fails to start

Symptom: npx my-api-mcp mcp start errors immediately.

Cause: Missing or invalid authentication flags.

Fix:

# Ensure auth flag matches your API's auth scheme
npx my-api-mcp mcp start --bearer-auth "YOUR_TOKEN"

# Check --help for available auth flags
npx my-api-mcp mcp start --help

No tools appear in AI assistant

Symptom: MCP server starts but AI assistant shows no tools.

Cause: Missing x-speakeasy-mcp extensions or all operations disabled.

Fix: Verify the scopes overlay is listed in workflow.yaml under overlays: and that operations have disabled: false.

Generation fails with mcp-typescript target

Symptom: speakeasy run fails when using target: mcp-typescript.

Cause: Usually a spec validation issue, missing workflow config, or using the deprecated enableMCPServer flag instead of the mcp-typescript target.

Fix:

# Validate spec first
speakeasy lint openapi --non-interactive -s ./openapi.yaml

# Ensure workflow.yaml uses target: mcp-typescript (NOT target: typescript with enableMCPServer)
cat .speakeasy/workflow.yaml

# Remove enableMCPServer from gen.yaml if present -- it is deprecated

Tools missing expected operations

Symptom: Some API operations are not available as MCP tools.

Cause: Operations not targeted by the scopes overlay or explicitly disabled.

Fix: Review mcp-scopes-overlay.yaml target selectors. Ensure paths and methods match your spec.

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