Create credential

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

The description adds meaningful behavior beyond annotations: it explains that secrets belong only in the data input, are excluded from logs/output, and that the tool returns metadata only. It also clarifies that isResolvable is forwarded only when supplied, giving the agent concrete operational expectations beyond the readOnly/write flags.

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 three dense sentences, each earning its place. It front-loads the core purpose, then layers preconditions, guidance, and security behavior without fluff. It is appropriately sized for the tool's complexity.

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 tool's complexity and the presence of an output schema, the description covers all essential context: prerequisite schema lookup, required mode/permission, secret handling, response shape, and how to handle existing credentials. No significant gaps remain.

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?

Even though schema coverage is 100%, the description adds semantic depth: it clarifies that 'name is only the stored label,' that isResolvable is forwarded only when supplied, and that data values are never returned. These insights go beyond the raw schema descriptions, helping the agent construct correct requests.

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 opens with 'Create and persist one credential as an additive write,' which identifies the specific verb, resource, and additive nature. It also explicitly distinguishes itself from the update sibling by naming n8n_credentials_update for existing credentials, clarifying its unique scope.

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?

Provides clear sequencing guidance: first call n8n_credentials_schema with the planned type, then build data from its field contract. It explicitly directs users to n8n_credentials_update for existing credentials and states the required mode/permission, offering both when-to-use and when-not-to-use guidance.

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