messages

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description's job is to add operational context — and it does: a 500-message ceiling, the semantics of the `images` count, and the important caveat that videos and files are only signaled rather than returned. It does not discuss pagination or failure behavior, which keeps it short of a 5.

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 two-mode structure is front-loaded: identity of the resource first, then the no-argument behavior, then the filtered behavior. Sentences are dense but each carries distinct information (limits, unread counts, attachment handling) rather than 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 responsibly sketches the return shape (contact, date, unread flag) and the attachment policy. For a 4-parameter tool at 0% schema coverage this is close to complete; missing only default-value explanations and any error/empty-result 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 description coverage is 0%, so the description carries the full burden and largely succeeds: `limit` is bounded at 500, `images` defaults toward returned photos with 0 meaning none, `contact` is identified as a directory name, and `conversation` takes an integer ID. Only the numeric defaults (15, 4) are left unexplained, which is a minor gap.

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 concrete resource ('SMS et RCS du téléphone') and spells out its two operating modes — recent-conversation listing vs. per-conversation message retrieval — so an agent immediately knows what it returns. The verb is only implied rather than stated, and no sibling tool is named, but the sibling set (files, notifications, phone) shows little overlap, so differentiation is not critical.

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?

It clearly states the conditions that select each mode: no argument yields recent conversations with contact/date/unread, while conversation=N or contact="Alice" yields the last `limit` messages. There are no explicit exclusions or named alternatives, but the branch conditions make usage unambiguous in practice.

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