n8n MCP Server

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries the full burden. It discloses important behavioral traits: the license requirement and the prerequisite to use 'init-n8n' first. It also warns about argument formatting ('Arguments must be provided as compact, single-line JSON without whitespace or newlines'). However, it doesn't cover aspects like rate limits, error handling, or what the output looks like (since there's no output schema), leaving some gaps in behavioral understanding.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is appropriately sized and front-loaded, starting with the core purpose. Each sentence adds value: the purpose, license requirement, usage timing, and argument formatting. There's no wasted text, and it's structured logically, though it could be slightly more polished for a perfect score.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the complexity (a list operation with 1 parameter), no annotations, and no output schema, the description is partially complete. It covers usage prerequisites and behavioral constraints but lacks parameter semantics and output details. For a tool with no structured support, it should do more to explain the parameter and expected results, making it only adequate.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema has 1 parameter ('clientId') with 0% description coverage, meaning the schema provides no semantic information. The description does not explain what 'clientId' is, its purpose, or how to obtain it. It only mentions argument formatting without adding meaning to the parameter itself. This fails to compensate for the low schema coverage, resulting in a poor score.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's purpose: 'List all variables from n8n.' It specifies the verb ('List') and resource ('variables from n8n'), making the action clear. However, it doesn't explicitly differentiate from sibling tools like 'create-variable' or 'delete-variable' beyond the obvious list vs. create/delete distinction, which is why it doesn't reach a perfect score.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides clear context for when to use the tool: 'Use after init-n8n to see available variables.' This gives a prerequisite and timing guidance. It also mentions a requirement ('Requires n8n Enterprise license with variable management features enabled'), which helps in decision-making. However, it doesn't explicitly state when not to use it or name alternatives, so it falls short of a 5.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.