Read a message

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

No annotations are provided, so the description carries the full burden. It discloses the read-only nature, the detection of verification codes, the listing of attachment metadata, and the conditional saving behavior with the caveat 'where the provider supports downloads'. This gives the agent a solid behavioral model of the tool's side effects.

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?

Two sentences with no fluff: the main purpose is front-loaded, and the optional save behavior is stated concisely with the provider-support caveat. Every sentence adds value.

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 simple read tool with three parameters and no output schema, the description covers what is returned (body, verification code, attachment metadata) and the optional disk-saving behavior. It does not explain error cases or how it relates to wait_for_code, but these are minor gaps given the tool's simplicity.

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 coverage is 100%, so the schema fully documents all three parameters. The description adds some context for save_dir (specifying it also saves the HTML body) and implies id comes from list_messages, but these are incremental beyond the schema. The baseline of 3 is appropriate.

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 clearly states a specific verb and resource: 'Read the full body of a message by id'. It also adds distinctive details (verification code detection, attachment metadata) that differentiate it from siblings like list_messages and wait_for_code.

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?

The description implies when to use the tool (to read the full body of a message) and mentions an optional save behavior, but it does not explicitly contrast it with siblings like wait_for_code or list_messages. No when-not-to-use guidance is provided.

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