mail_search

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

Goes well beyond the annotations: it discloses that Spam/Trash and Message-ID-less messages are omitted, that hasAttachment only filters within the newest `limit` results (so counts can be short or empty), and it carries an explicit prompt-injection warning about treating email content as untrusted data. The read-only sentence reinforces the hints with concrete operations that are never performed.

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?

Four dense sentences, front-loaded with the safety posture and the injection warning before mechanics. Slight redundancy in restating read-only behavior already covered by annotations, but nothing is 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 steps in to describe the return shape (refs plus date, sender, subject, attachment info) and the omission rules. Gaps remain around result ordering, pagination beyond `limit`, and how `mailbox` relates to the allowlist.

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 0% across 7 parameters, so the description must carry the burden. It adds real meaning for hasAttachment and its interaction with limit, but from, since, before, mailbox and subject are never explained (matching semantics, exact vs substring, date inclusivity).

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+resource ("Searches the allowlisted mailbox") and even enumerates the returned fields (refs, date, sender, subject, attachment info). It is clearly a search tool rather than a message reader, but it never names mail_read or mail_list_mailboxes to sharpen the boundary.

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?

Usage is implied by the filter set and the scope note ("allowlisted mailbox"), and the hasAttachment caveat implies a recommended query pattern. However, there is no explicit when-to-use / when-not guidance and no routing to siblings like mail_read for full message bodies.

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