What causes "unable to retrieve enableDraftSpecs from context" in googleapis/mcp-toolbox?

Ensure requests go through the standard server handler that injects the enableDraftSpecs value into the context (util.WithEnableDraftSpecs or equivalent).

googleapis/mcp-toolbox · error · jsonrpc.Error

INTERNAL_ERROR

INTERNAL_ERROR

Error message

unable to retrieve enableDraftSpecs from context

What it means

ProcessMethod reads the enableDraftSpecs flag from the request context via util.EnableDraftSpecsFromContext; if the value was never injected into the context (it should be set by the HTTP handler middleware before dispatch), it returns an INTERNAL_ERROR. This indicates an internal wiring bug rather than a client mistake.

Source

Thrown at internal/server/mcp/mcp.go:62

// NotificationHandler process notifications request. It MUST NOT send a response.
// Currently Toolbox does not process any notifications.
func NotificationHandler(ctx context.Context, body []byte) error {
	var notification jsonrpc.JSONRPCNotification
	if err := json.Unmarshal(body, &notification); err != nil {
		return fmt.Errorf("invalid notification request: %w", err)
	}
	// Since we do not enforce notifications, we do not need to check the
	// `Mcp-Method` header here
	return nil
}

// ProcessMethod returns a response for the request.
// This is the Operation phase of the lifecycle for MCP client-server connections.
func ProcessMethod(ctx context.Context, mcpVersion string, id jsonrpc.RequestId, method string, g group.Group, primitiveMgr *primitives.PrimitiveManager, 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
	}
	switch mcpVersion {
	case mcputil.VERSION_20260728:
		return v20260728.ProcessMethod(ctx, id, method, g, primitiveMgr, body, header)
	case mcputil.VERSION_20251125:
		return v20251125.ProcessMethod(ctx, id, method, g, primitiveMgr, body, header)
	case mcputil.VERSION_20250618:
		return v20250618.ProcessMethod(ctx, id, method, g, primitiveMgr, body, header)
	case mcputil.VERSION_20250326:
		return v20250326.ProcessMethod(ctx, id, method, g, primitiveMgr, body, header)
	case "", mcputil.VERSION_20241105:
		return v20241105.ProcessMethod(ctx, id, method, g, primitiveMgr, body, header)
	default:
		return jsonrpc.NewUnsupportedProtocolVersionError(id, mcpVersion, enableDraft)
	}
}

View on GitHub (pinned to 8cc6e09de2)

Solutions

Ensure requests go through the standard server handler that injects the enableDraftSpecs value into the context (util.WithEnableDraftSpecs or equivalent).
If calling ProcessMethod directly, add the flag to the context first: ctx = util.WithEnableDraftSpecs(ctx, true|false).
Update the toolbox binary/server wiring if you patched or forked internal handlers.
Report/inspect upstream if a stock server path reproduces this — it signals missing middleware in that path.

Example fix

// before: direct call with a plain context
res, err := mcp.ProcessMethod(ctx, ver, id, method, g, pmgr, body, hdr)
// after: inject the draft-specs flag expected by ProcessMethod
ctx = util.WithEnableDraftSpecs(ctx, false)
res, err := mcp.ProcessMethod(ctx, ver, id, method, g, pmgr, body, hdr)

Defensive patterns

Strategy: try-catch

Validate before calling

_, ok := util.EnableDraftSpecsFromContext(ctx)
if !ok {
    ctx = util.WithEnableDraftSpecs(ctx, false)
}

Try / catch

res, err := mcp.ProcessMethod(ctx, ver, id, method, g, pmgr, body, hdr)
if err != nil && strings.Contains(err.Error(), "enableDraftSpecs") {
    ctx = util.WithEnableDraftSpecs(ctx, false)
    res, err = mcp.ProcessMethod(ctx, ver, id, method, g, pmgr, body, hdr)
}

Prevention

Route all MCP traffic through the stock HTTP handler that injects context values
In tests, always build contexts with util.WithEnableDraftSpecs before calling ProcessMethod
Treat INTERNAL_ERROR responses as server wiring bugs and check middleware setup first

When it happens

Trigger: Calling ProcessMethod directly (tests, custom embeddings) with a bare context.Context that lacks the enableDraftSpecs value; a server code path that builds the context without running the middleware that stores the flag.

Common situations: Custom forks or wrappers around the MCP server that bypass the standard httpHandler; unit/integration tests constructing requests manually; upgrades where middleware registration was dropped.

Related errors

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/1ca65de9afe205f1. Report an issue: GitHub.