ChainFETCH MCP Server

Instructions

Implementation Reference

• index.js:526-565 (registration)

  Registration of the 'search_smart_contracts_json' tool in the ListTools response, including name, description, and input schema definition.

  {
    name: 'search_smart_contracts_json',
    description: 'JSON search for smart contracts with 50+ parameters',
    inputSchema: {
      type: 'object',
      properties: {
        is_verified: {
          type: 'boolean',
          description: 'Whether the contract is verified',
        },
        name: {
          type: 'string',
          description: 'Contract name',
        },
        language: {
          type: 'string',
          description: 'Programming language (e.g., "solidity")',
        },
        proxy_type: {
          type: 'string',
          description: 'Proxy type (e.g., "eip1967")',
        },
        optimization_enabled: {
          type: 'boolean',
          description: 'Whether optimization is enabled',
        },
        limit: {
          type: 'integer',
          description: 'Number of results to return (default: 10, max: 50)',
          default: 10,
        },
        offset: {
          type: 'integer',
          description: 'Number of results to skip for pagination (default: 0)',
          default: 0,
        },
      },
      required: [],
    },
  },

• index.js:762-763 (handler)

  Handler case in handleToolCall method that executes the tool by calling makeRequest to proxy the API call to ChainFETCH's json_search endpoint for smart contracts.

  case 'search_smart_contracts_json':
    return await this.makeRequest('/api/v1/ethereum/smart-contracts/json_search', 'GET', args, null, token);

• index.js:634-682 (helper)

  Helper method makeRequest that handles the actual HTTP API calls to ChainFETCH, used by all tool handlers including search_smart_contracts_json.

  async makeRequest(endpoint, method = 'GET', params = {}, body = null, token = null) {
    const chainfetchToken = token || process.env.CHAINFETCH_API_TOKEN;
    
    if (!chainfetchToken) {
      throw new McpError(
        ErrorCode.InvalidRequest,
        'CHAINFETCH_API_TOKEN is required'
      );
    }
  
    const url = new URL(`${API_BASE_URL}${endpoint}`);
    
    // Add query parameters for GET requests
    if (method === 'GET' && Object.keys(params).length > 0) {
      Object.entries(params).forEach(([key, value]) => {
        if (value !== undefined && value !== null) {
          if (Array.isArray(value)) {
            value.forEach(v => url.searchParams.append(`${key}[]`, v));
          } else {
            url.searchParams.append(key, value.toString());
          }
        }
      });
    }
  
    const fetchOptions = {
      method,
      headers: {
        'Authorization': `Bearer ${chainfetchToken}`,
        'Content-Type': 'application/json',
      },
    };
  
    if (body && method !== 'GET') {
      fetchOptions.body = JSON.stringify(body);
    }
  
    const response = await fetch(url.toString(), fetchOptions);
    
    if (!response.ok) {
      const errorText = await response.text();
      throw new McpError(
        ErrorCode.InternalError,
        `API request failed: ${response.status} ${response.statusText} - ${errorText}`
      );
    }
  
    return await response.json();
  }