messages

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

With no annotations, the description carries the full burden and does well: it discloses the return content (contact, date, unread counts; messages; attached photos), the 500-message cap, and that videos/files are only flagged rather than returned. It omits any statement about read-only nature, permission requirements, or error behavior, which keeps it from 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?

Front-loaded with the resource (SMS et RCS du téléphone) and then branches cleanly into the two modes. Dense but every clause carries information; only the backtick notation is slightly noisy.

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 4-parameter tool with no output schema, no annotations, and 0% schema coverage, the description covers both invocation modes, all parameters, output fields, and result caps. Remaining gaps (permissions, side-effect profile, error cases) are minor for an obviously read-oriented tool.

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 must compensate, and it largely does: limit (last N messages, max 500), images (count of most recent photos, 0 for none), contact (directory name), and conversation (numeric id) are all given meaning. Defaults and types are left to the schema, so not quite complete.

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: retrieving SMS/RCS messages from the phone, with two distinct operating modes spelled out. It does not explicitly differentiate itself from siblings like phone, notifications, or look, so it stops short of a 5.

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?

Gives clear conditional guidance: no argument yields recent conversations, while conversation=N or contact="Alice" yields the last messages. This tells the agent exactly how to choose between invocation modes, though it offers no comparison against sibling tools that might also surface phone data.

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