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

Annotations already cover readOnly, idempotent and non-destructive, and the description reinforces 'Read-only' while adding genuinely new behavior: the response includes URL, events and active status, and the signing secret is never returned. That secret-masking note is a real disclosure an agent can't get from annotations or schema.

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?

Two tight sentences: what is returned first, then the secret caveat and the read-only/parameter note. Zero redundant wording and the key information is front-loaded.

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 usefully previews the return shape (URL, events, active) and flags the omitted secret, which is what an agent needs to interpret the response. A minor gap remains around error behavior for an unknown ID, but otherwise it is complete for a simple single-record read.

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 description coverage is 100% for the single webhook_id parameter, so the schema already carries the semantics. The description only restates that webhook_id is required, adding no format or sourcing detail (e.g., where to obtain the ID). Baseline 3 applies.

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 ('Get details of one transactional (Email API) webhook') and enumerates the returned fields (URL, events, active flag). The qualifier 'one' plus 'transactional (Email API)' separates it from list_transactional_webhooks and from the generic get_webhook sibling.

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 phrase 'needs webhook_id' implies a single-record lookup by ID, which implicitly contrasts with the list tool, but the description never says when to prefer this over list_transactional_webhooks or get_webhook, and gives no prerequisites. Usage is implied rather than stated.

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