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

Annotations cover the safety profile (non-read-only, idempotent, non-destructive), so the bar is lower. The description adds genuinely useful undisclosed behavior: a new URL returns webhook_signing_secret exactly once, that secret must be shared privately, and the endpoint should verify X-Railagent-Signature. Minor gap: no mention of what happens when an existing URL is re-set.

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?

Three short sentences, front-loaded with the purpose, then the security constraint and the return-value caveat. Every sentence carries distinct information with no padding.

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?

With no output schema, the description helpfully covers the one-time webhook_signing_secret return and the signature-verification expectation. For a 3-parameter, non-destructive write tool this is nearly complete; it only lacks guidance on re-setting an existing URL and validation failure behavior.

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?

Schema coverage is 100%, so the schema already documents all three parameters, establishing a baseline of 3. The description reinforces the HTTPS requirement for webhook_url and introduces the signing-secret/signature flow, but adds little beyond what the schema's own field descriptions provide.

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?

States a specific verb and resource ('Set an HTTPS webhook') and explains its purpose ('so the inbox can notify it of new mail in realtime'). It does not explicitly differentiate from the sibling test_webhook, so it falls short of a 5.

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?

Implies usage (register an endpoint so the inbox can push new-mail events) and adds a security caveat about not sharing the key, but never states when to use this versus test_webhook or other alternatives, nor any prerequisites beyond HTTPS.

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