MCP Methods Reference

Complete reference for all Model Context Protocol methods exposed by MA²D servers.

Overview

MCP defines a set of JSON-RPC 2.0 methods for interacting with servers. All methods follow the same request/response pattern.

Method List

Method	Description	Parameters	Returns
`initialize`	Negotiate capabilities	clientInfo, capabilities	serverInfo, capabilities
`tools/list`	List available tools	none	Array of tools
`tools/call`	Execute a tool	name, arguments	Tool result
`resources/list`	List available resources	none	Array of resources
`resources/read`	Read resource content	uri	Resource content
`prompts/list`	List available prompts	none	Array of prompts
`prompts/get`	Get prompt template	name, arguments	Prompt with messages

initialize

Negotiate protocol capabilities between client and server.

Request

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "initialize",
  "params": {
    "protocolVersion": "2024-11-05",
    "clientInfo": {
      "name": "my-client",
      "version": "1.0.0"
    },
    "capabilities": {}
  }
}

Parameters

protocolVersion (string, required) - MCP protocol version
clientInfo (object, required)
- name (string) - Client name
- version (string) - Client version
capabilities (object, optional) - Client capabilities

Response

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "protocolVersion": "2024-11-05",
    "serverInfo": {
      "name": "weather-api",
      "version": "1.0.0"
    },
    "capabilities": {
      "tools": {},
      "resources": {},
      "prompts": {}
    }
  }
}

Response Fields

protocolVersion - Server’s protocol version
serverInfo - Server metadata
capabilities - What the server supports

tools/list

Retrieve all available tools from the server.

Request

{
  "jsonrpc": "2.0",
  "id": 2,
  "method": "tools/list"
}

Parameters

None

Response

{
  "jsonrpc": "2.0",
  "id": 2,
  "result": {
    "tools": [
      {
        "name": "get_weather",
        "description": "Get current weather conditions for a city",
        "inputSchema": {
          "type": "object",
          "properties": {
            "city": {
              "type": "string",
              "description": "City name"
            },
            "units": {
              "type": "string",
              "enum": ["celsius", "fahrenheit"]
            }
          },
          "required": ["city"]
        }
      }
    ]
  }
}

Response Fields

tools (array) - List of available tools
- name - Tool identifier
- description - What the tool does
- inputSchema - JSON Schema for parameters

tools/call

Execute a specific tool with provided arguments.

Request

{
  "jsonrpc": "2.0",
  "id": 3,
  "method": "tools/call",
  "params": {
    "name": "get_weather",
    "arguments": {
      "city": "San Francisco",
      "units": "fahrenheit"
    }
  }
}

Parameters

name (string, required) - Tool name to execute
arguments (object, required) - Tool parameters

Response

{
  "jsonrpc": "2.0",
  "id": 3,
  "result": {
    "content": [
      {
        "type": "text",
        "text": "{\"city\":\"San Francisco\",\"temperature\":65,\"units\":\"fahrenheit\",\"conditions\":\"Partly cloudy\"}"
      }
    ]
  }
}

Response Fields

content (array) - Tool execution results
- type - Content type (text, image, resource)
- text - Content data (for text type)

resources/list

Get all available resources from the server.

Request

{
  "jsonrpc": "2.0",
  "id": 4,
  "method": "resources/list"
}

Parameters

None

Response

{
  "jsonrpc": "2.0",
  "id": 4,
  "result": {
    "resources": [
      {
        "uri": "weather://cities/supported",
        "name": "Supported Cities",
        "description": "List of cities with weather data",
        "mimeType": "application/json"
      }
    ]
  }
}

Response Fields

resources (array) - Available resources
- uri - Resource identifier
- name - Human-readable name
- description - Resource description
- mimeType - Content type

resources/read

Read the content of a specific resource.

Request

{
  "jsonrpc": "2.0",
  "id": 5,
  "method": "resources/read",
  "params": {
    "uri": "weather://cities/supported"
  }
}

Parameters

uri (string, required) - Resource URI to read

Response

{
  "jsonrpc": "2.0",
  "id": 5,
  "result": {
    "contents": [
      {
        "uri": "weather://cities/supported",
        "mimeType": "application/json",
        "text": "{\"cities\":[{\"name\":\"San Francisco\",\"country\":\"USA\"}]}"
      }
    ]
  }
}

Response Fields

contents (array) - Resource content
- uri - Resource URI
- mimeType - Content type
- text - Resource data

prompts/list

List all available prompt templates.

Request

{
  "jsonrpc": "2.0",
  "id": 6,
  "method": "prompts/list"
}

Parameters

None

Response

{
  "jsonrpc": "2.0",
  "id": 6,
  "result": {
    "prompts": [
      {
        "name": "weather_query",
        "description": "Generate weather query prompt",
        "arguments": [
          {
            "name": "city",
            "description": "City to query",
            "required": true
          }
        ]
      }
    ]
  }
}

Response Fields

prompts (array) - Available prompts
- name - Prompt identifier
- description - Prompt purpose
- arguments - Required parameters

prompts/get

Get a specific prompt with argument substitution.

Request

{
  "jsonrpc": "2.0",
  "id": 7,
  "method": "prompts/get",
  "params": {
    "name": "weather_query",
    "arguments": {
      "city": "San Francisco"
    }
  }
}

Parameters

name (string, required) - Prompt name
arguments (object, optional) - Prompt arguments

Response

{
  "jsonrpc": "2.0",
  "id": 7,
  "result": {
    "description": "Weather query for San Francisco",
    "messages": [
      {
        "role": "user",
        "content": {
          "type": "text",
          "text": "What's the weather in San Francisco?"
        }
      }
    ]
  }
}

Response Fields

description - Prompt description
messages - Array of message objects
- role - Message role (user/assistant/system)
- content - Message content

Error Responses

All methods can return errors following JSON-RPC 2.0:

{
  "jsonrpc": "2.0",
  "id": 1,
  "error": {
    "code": -32602,
    "message": "Invalid params",
    "data": {
      "details": "Missing required parameter: city"
    }
  }
}

Standard Error Codes

Code	Name	Description
-32700	Parse error	Invalid JSON
-32600	Invalid request	Malformed JSON-RPC
-32601	Method not found	Unknown method
-32602	Invalid params	Bad parameters
-32603	Internal error	Server error
-32001	Unauthorized	Authentication failed

See MCP Endpoints for endpoint details.

Protocol Compliance

MA²D servers follow MCP specification 2024-11-05:

✅ JSON-RPC 2.0 format
✅ HTTP-Streamable transport
✅ Server-Sent Events (SSE)
✅ All required methods
✅ Standard error codes
✅ JSON Schema validation

Best Practices

Request IDs

Use unique, incrementing IDs:

let requestId = 1
const request = {
  jsonrpc: '2.0',
  id: requestId++,
  method: 'tools/list'
}

Parameter Validation

Validate against input schemas:

import Ajv from 'ajv'
 
const ajv = new Ajv()
const validate = ajv.compile(tool.inputSchema)
 
if (!validate(arguments)) {
  throw new Error(ajv.errorsText(validate.errors))
}

Error Handling

Always check for errors:

const data = await response.json()
 
if (data.error) {
  console.error(`Error ${data.error.code}: ${data.error.message}`)
  return
}
 
processResult(data.result)

Next Steps

MCP Endpoints - Multi-language endpoint examples
Consuming MCP via REST API - REST API guide

External Resources

MCP Specification - Official protocol docs
JSON-RPC 2.0 - RPC specification
JSON Schema - Schema validation

Reference Version: MCP 2024-11-05
Last Updated: January 2026

Overview Agent Card Specification