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

With no annotations, the description carries the full burden and does so well: delete is a soft disable (sets disabled_at, row stays), create returns the signing secret exactly once, calls do not meter and do not send email, and ACLs are named per action. These are non-obvious behaviors an agent could not infer from the 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?

The description is dense but front-loaded with the most important constraint (metadata only, no body), then walks through actions in order. It is a single long paragraph, so it is slightly harder to scan than a bulleted structure would be, but nearly every sentence carries information.

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?

For a four-action tool with no annotations and no output schema, the description covers per-action semantics, the one-time secret, soft-delete behavior, and non-metering. It does not describe the shape of list/deliveries results, but with no output schema that is the only meaningful residual gap.

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%, so the schema already documents url, limit, offset, secret, status, and webhookId per action. The description largely restates the same routing (create/list/delete/deliveries) and adds no format or syntax detail beyond the schema, so the 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?

The description names a specific resource (HTTPS webhooks for email.received metadata) and enumerates the four operations it multiplexes via action. It also explicitly excludes the message body and routes the agent away from the sibling manage_inbox, so the tool's identity is unambiguous.

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?

Each action is documented with its effect and the ACL it checks, which tells the agent exactly which action to pick for which goal. It closes with an explicit alternative ('Use manage_inbox for the inbox itself') and clarifies that later delivery attempts are not part of this call.

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