googleapis/mcp-toolbox · error

INTERNAL_ERROR

INTERNAL_ERROR

Error message

unable to retrieve enableDraftSpecs from context

What it means

serverDiscoverHandler reads the enableDraftSpecs flag from the request context via util.EnableDraftSpecsFromContext; it must always be present for server/discover requests. If missing, the context was not populated by the middleware/route that normally injects it, so the handler returns a jsonrpc INTERNAL_ERROR rather than guessing a default (internal/server/mcp/v20260728/method.go:167).

Source

Thrown at internal/server/mcp/v20260728/method.go:167

		return resMeta, nil
	}

	newMeta := make(map[string]any)
	// copy current Metadata into the new meta obj
	for k, v := range curMeta {
		newMeta[k] = v
	}
	// copy the ResultMetaObject items over
	for k, v := range resMeta {
		newMeta[k] = v
	}
	return newMeta, nil
}

func serverDiscoverHandler(ctx context.Context, id jsonrpc.RequestId, body []byte, header http.Header) (any, error) {
	enableDraft, ok := util.EnableDraftSpecsFromContext(ctx)
	if !ok {
		err := fmt.Errorf("unable to retrieve enableDraftSpecs from context")
		return jsonrpc.NewError(id, jsonrpc.INTERNAL_ERROR, err.Error(), nil), err
	}

	var req DiscoverRequest
	if err := json.Unmarshal(body, &req); err != nil {
		err = fmt.Errorf("invalid server discover request: %w", err)
		return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, err.Error(), nil), err
	}
	validateHeaderErr, err := validateHeader(id, header, SERVER_DISCOVER, "")
	if err != nil {
		return validateHeaderErr, err
	}
	validateErr, err := validateMetadata(id, req.Params, header == nil)
	if err != nil {
		return validateErr, err
	}

	toolsListChanged := false

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Route the request through the standard MCP server wiring so the middleware that injects enableDraftSpecs runs.
2. In tests or custom handlers, populate the context with util.WithEnableDraftSpecs(ctx, <bool>) before calling serverDiscoverHandler.
3. Update to a current toolbox version if you maintain a patched fork where the context-injection middleware was removed.

Example fix

// before
handler(ctx, id, body, header) // ctx lacks the flag
// after
ctx = util.WithEnableDraftSpecs(ctx, true)
handler(ctx, id, body, header)

// Go: ensure the context carries the flag before invoking the handler
if _, ok := util.EnableDraftSpecsFromContext(ctx); !ok {
    ctx = util.WithEnableDraftSpecs(ctx, false)
}

res, err := serverDiscoverHandler(ctx, id, body, header)
if err != nil && strings.Contains(err.Error(), "unable to retrieve enableDraftSpecs") {
    // handler was invoked without the standard middleware; reroute or fix wiring
    log.Printf("misconfigured handler wiring: %v", err)
}

When it happens

Trigger: Invoking serverDiscoverHandler through a custom route, test harness, or ProcessMethod path that bypasses the middleware which calls util.WithEnableDraftSpecs (or equivalent) to store the flag in ctx.

Common situations: Custom HTTP handlers wrapping the MCP processor without the spec-version middleware; unit/integration tests constructing a context manually; framework adapters that create a fresh context.Context for handlers.

Related errors

• INTERNAL_ERROR
• INTERNAL_ERROR
• unable to retrieve logger: %w
• INTERNAL_ERROR
• METHOD_NOT_FOUND

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/a0c62097dfc09d88. Report an issue: GitHub.