proxy-mcp

Instructions

Implementation Reference

• src/tools/modification.ts:22-53 (handler)

  The handler function for the proxy_inject_headers tool, which processes input parameters, constructs a rule matcher and handler, and adds the rule via the proxyManager.

  async ({ hostname, url_pattern, headers, direction, priority }) => {
    try {
      const matcher: RuleMatcher = {};
      if (hostname) matcher.hostname = hostname;
      if (url_pattern) matcher.urlPattern = url_pattern;
  
      const handler: RuleHandler = { type: "passthrough" };
      if (direction === "request" || direction === "both") {
        handler.transformRequest = { updateHeaders: headers };
      }
      if (direction === "response" || direction === "both") {
        handler.transformResponse = { updateHeaders: headers };
      }
  
      const rule = await proxyManager.addRule({
        priority,
        enabled: true,
        description: `Inject headers: ${Object.keys(headers).join(", ")} (${direction})`,
        matcher,
        handler,
      });
  
      return {
        content: [{
          type: "text",
          text: JSON.stringify({ status: "success", rule_id: rule.id, description: rule.description }),
        }],
      };
    } catch (e) {
      return { content: [{ type: "text", text: JSON.stringify({ status: "error", error: String(e) }) }] };
    }
  },

• src/tools/modification.ts:11-21 (registration)

  Registration and schema definition for the proxy_inject_headers tool, using Zod for parameter validation.

  server.tool(
    "proxy_inject_headers",
    "Add or overwrite headers on matching traffic. Creates a passthrough rule with header transforms.",
    {
      hostname: z.string().optional().describe("Hostname to match (optional)"),
      url_pattern: z.string().optional().describe("URL regex pattern to match (optional)"),
      headers: z.record(z.string().nullable()).describe("Headers to inject (key-value pairs, set value to null to delete a header)"),
      direction: z.enum(["request", "response", "both"]).optional().default("request")
        .describe("Where to inject: request, response, or both"),
      priority: z.number().optional().default(50).describe("Rule priority (default: 50)"),
    },