mail_get_message

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

Goes well beyond annotations: it discloses that complete body parts are written to private local files, that HTML is returned as inert non-executed text, that mail content is untrusted data and never instructions, and that results over 64 KiB are persisted to a private JSON file with a compact summary plus completeResultFile. Annotations cover the read-only/idempotent safety profile, and the description layers substantial operational and security context on top.

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?

Five sentences, all load-bearing, with the payload description front-loaded before the storage/truncation and security notes. No filler, though the density means a few clauses (the file-saving behavior) could be tightened.

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 does a good job describing returns (previews, partId downloads, completeResultFile) and safety posture. But for an 8-parameter tool with 0% schema coverage it leaves every input parameter unexplained, including the required uidValidity, which an agent cannot infer from the name alone.

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 8 parameters, so the description carries the full burden of explaining maxBodyParts, previewBytes, includeBodies, headerPreviewBytes, and the four required addressing fields (accountId, folder, uid, uidValidity). It names none of them, only describing outputs like partId and completeResultFile; 'bounded text/HTML previews' hints at previewBytes but gives no units, defaults, or limits.

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 (read a message) and enumerates the payload shape: server metadata, duplicate-preserving ordered headers, MIME structure, and bounded text/HTML previews. It is clearly differentiated from mail_download_raw by the 'download the raw .eml for original bytes' pointer, though it never distinguishes itself from the singular-vs-plural sibling mail_get_messages.

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 through embedded pointers ('Other MIME parts are downloadable by partId', 'download the raw .eml for original bytes'), which gestures at mail_download_attachment and mail_download_raw. However there is no explicit when-to-use/when-not statement, no prerequisite description (e.g. needing uidValidity), and no direct callout of the sibling this replaces.

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