proxy_inject_headers

Modify HTTP traffic by adding, overwriting, or deleting headers in requests or responses based on hostname or URL patterns.

Instructions

Add or overwrite headers on matching traffic. Creates a passthrough rule with header transforms.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`hostname`	No	Hostname to match (optional)
`url_pattern`	No	URL regex pattern to match (optional)
`headers`	Yes	Headers to inject (key-value pairs, set value to null to delete a header)
`direction`	No	Where to inject: request, response, or both	request
`priority`	No	Rule priority (default: 50)

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)"),
  },

proxy-mcp