The n8n MCP server has a single tool 'n8n_workflow' with significant structural and documentation gaps. The tool name does not follow verb-noun conventions (should be 'execute_workflow'), the description is minimal (22 chars), parameter descriptions are present but lack implementation context or validation guidance, and there is no documented output schema. The input schema visible in code shows basic JSON schema structure but lacks type constraints, enums, or detailed parameter documentation. The server appears to be an early-stage implementation with no error handling patterns, no output structure guidance, and no evidence of production-grade tool design. Based on rubric calibration, this falls in the F-D range (0-49) due to missing descriptions (<20 chars baseline violation), no output schema, and non-idiomatic naming.

• Rename 'n8n_workflow' to 'execute_workflow' or 'run_workflow'. Tool names must start with an action verb so LLMs understand intent from the name alone.
• Expand description from 22 chars to 100-150 chars. Include: what the tool does (executes n8n workflow definitions), when to use it (when you need to automate a process defined in n8n), what inputs are required (workflow nodes and connections), and what the result contains. Example: 'Execute an n8n workflow by providing its node definitions and connections. Returns the execution result with output from the final node. Use this to automate multi-step processes. Requires valid n8n workflow structure (nodes array and connections map).'
• Document the output schema explicitly in the description and/or in a separate 'returns' section. Specify: does it return { success: bool, result: any, errors: array }? What are the top-level fields? Example: 'Returns { status: string (success|error), result: any, executionId: string, timestamp: ISO8601 }'
• Add type constraints and properties to 'workflowData' parameter. Define expected structure: { nodes: array, connections: object, name?: string }. Specify that nodes must have 'id' and 'type' fields.
• Add constraints to 'inputData' parameter. Explain that it should match the input keys expected by the workflow's first node. Provide validation rules or a link to n8n workflow input schema documentation.
• Implement structured error responses. Examples: 'Workflow validation failed: missing node IDs' (user-fixable, suggest fixing workflow), 'N8N service unreachable' (retryable, suggest retry), 'Workflow execution timeout (30s)' (suggest increasing timeout or simplifying workflow).