DriftOS MCP Server

Instructions

Implementation Reference

• src/tools/context.ts:71-127 (registration)

  Complete registration of the 'driftos_build_prompt' MCP tool, including schema, description, and inline handler function that delegates to driftClient.buildPrompt.

    server.registerTool(
      'driftos_build_prompt',
      {
        title: 'Build LLM Prompt',
        description: `Build a ready-to-use prompt for LLM calls with context and facts.
  
  Args:
    - branch_id (string): The branch ID to build prompt for
    - system_prompt (string, optional): Custom system prompt prefix
  
  Returns:
    {
      "system": string,  // Full system prompt with topic and facts
      "messages": [{ "role": string, "content": string }]  // Conversation messages
    }
  
  Use this to get a complete prompt ready for OpenAI/Anthropic/etc API calls.`,
        inputSchema: z.object({
          branch_id: z.string().min(1).describe('Branch ID to build prompt for'),
          system_prompt: z.string().optional().describe('Custom system prompt prefix'),
        }).strict(),
        annotations: {
          readOnlyHint: true,
          destructiveHint: false,
          idempotentHint: true,
          openWorldHint: false,
        },
      },
      async (params) => {
        try {
          const result = await driftClient.buildPrompt(
            params.branch_id,
            params.system_prompt
          );
  
          return {
            content: [
              {
                type: 'text' as const,
                text: JSON.stringify(result, null, 2),
              },
            ],
          };
        } catch (error) {
          const message = error instanceof Error ? error.message : 'Unknown error';
          return {
            content: [
              {
                type: 'text' as const,
                text: `Error building prompt: ${message}`,
              },
            ],
            isError: true,
          };
        }
      }
    );

• src/tools/context.ts:99-126 (handler)

  Inline handler function for executing the 'driftos_build_prompt' tool. It invokes driftClient.buildPrompt and returns the JSON-formatted result as MCP content, with error handling.

  async (params) => {
    try {
      const result = await driftClient.buildPrompt(
        params.branch_id,
        params.system_prompt
      );
  
      return {
        content: [
          {
            type: 'text' as const,
            text: JSON.stringify(result, null, 2),
          },
        ],
      };
    } catch (error) {
      const message = error instanceof Error ? error.message : 'Unknown error';
      return {
        content: [
          {
            type: 'text' as const,
            text: `Error building prompt: ${message}`,
          },
        ],
        isError: true,
      };
    }
  }

• src/tools/context.ts:73-98 (schema)

  Tool metadata and input schema using Zod: requires branch_id (string), optional system_prompt (string). Includes title, description, and annotations indicating read-only, idempotent behavior.

      {
        title: 'Build LLM Prompt',
        description: `Build a ready-to-use prompt for LLM calls with context and facts.
  
  Args:
    - branch_id (string): The branch ID to build prompt for
    - system_prompt (string, optional): Custom system prompt prefix
  
  Returns:
    {
      "system": string,  // Full system prompt with topic and facts
      "messages": [{ "role": string, "content": string }]  // Conversation messages
    }
  
  Use this to get a complete prompt ready for OpenAI/Anthropic/etc API calls.`,
        inputSchema: z.object({
          branch_id: z.string().min(1).describe('Branch ID to build prompt for'),
          system_prompt: z.string().optional().describe('Custom system prompt prefix'),
        }).strict(),
        annotations: {
          readOnlyHint: true,
          destructiveHint: false,
          idempotentHint: true,
          openWorldHint: false,
        },
      },

• src/services/drift-client.ts:4-4 (helper)

  Exports the driftClient instance, created from @driftos/client, which provides the buildPrompt method called by the tool handler.

  export const driftClient = createDriftClient(DRIFTOS_API_URL);