prometheus-mcp

Instructions

Implementation Reference

• src/prometheus/client.ts:218-221 (handler)

  Executes the tool logic by making an HTTP GET request to the Prometheus API endpoint `/api/v1/label/{label}/values` to retrieve all values for the specified label.

  async getLabelValues(label: string): Promise<LabelValues> {
    const endpoint = `/api/v1/label/${encodeURIComponent(label)}/values`;
    return this.request<LabelValues>(endpoint);
  }

• src/server/tools.ts:68-70 (schema)

  Zod schema defining the input parameters for the tool: a required 'label' string.

  const PrometheusLabelValuesSchema = z.object({
    label: z.string().describe("label name to get values for"),
  });

• src/server/tools.ts:123-131 (registration)

  Registers the tool in the tools array with metadata, schema, and handler function that delegates to PrometheusClient.getLabelValues.

  defineTool<typeof PrometheusLabelValuesSchema, LabelValues>({
    capability: "discovery",
    name: "prometheus_label_values",
    title: "Get Label Values",
    description: "Get all values for a specific Prometheus label",
    inputSchema: PrometheusLabelValuesSchema,
    type: "readonly",
    handle: async (client: PrometheusClient, args) => client.getLabelValues(args.label),
  }),

• src/server/server.ts:58-62 (registration)

  Registers filtered tools (including prometheus_label_values if discovery enabled) with the MCP server via _registerTool.

    const prometheusTools: ToolAny[] = tools.filter(
      (tool) => validatedConfig[capabilityMap[tool.capability]] ?? false,
    );
    prometheusTools.forEach((tool) => this._registerTool(tool));
  }

• src/prometheus/client.ts:52-92 (helper)

  Private helper method that performs all HTTP requests to Prometheus API, handles responses, errors, and logging.

  private async request<T>(
    endpoint: string,
    params?: Record<string, string>,
  ): Promise<T> {
    const url = new URL(endpoint, this.baseUrl);
    const queryParams = new URLSearchParams(params);
    if (queryParams) {
      url.search = queryParams.toString();
    }
    logger.debug("making prometheus request", { endpoint, url });
  
    try {
      const response = await fetch(url.toString(), {
        method: "GET",
        headers: this.headers,
      });
  
      if (!response.ok) {
        const error = `http ${response.status}: ${response.statusText}`;
        logger.error(error, { endpoint, status: response.status });
        throw new Error(error);
      }
  
      const result: Response<T> = await response.json();
  
      if (result.status !== "success") {
        const errorMsg = result.error || "unknown error";
        const error = `prometheus api error: ${errorMsg}`;
        logger.error(error, { endpoint, status: result.status });
        throw new Error(error);
      }
  
      logger.debug("prometheus request successful", { endpoint });
      return result.data;
    } catch (error) {
      logger.error("prometheus request failed", {
        endpoint,
        error: error instanceof Error ? error.message : String(error),
      });
      throw error;
    }