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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered; the description adds the valuable disclosure that responses contain metadata and the OTP but never the message body. It also adds the sort order, which matters when consuming results. It stops short of saying what metadata fields appear or whether results are paginated, but that is a minor gap given the annotations.

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 short sentences with no filler, and the most decision-relevant facts (scope and ordering) are front-loaded before the return-content clarification.

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 read-only listing tool with only two fully documented parameters, the description covers purpose, ordering, filtering, and return payload, which is enough to call it correctly. The only real omission is how the 50-message cap interacts with a short result set, i.e. whether truncation occurs, which is minor.

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 100%, so both `to` and `limit` are fully documented in the schema, including format, case-insensitivity, default, and bounds. The description only restates that the address filter is optional, adding essentially no meaning beyond the schema, so the baseline of 3 applies.

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 ("List recent messages") plus ordering ("newest first"), an optional scope ("only those sent to one address"), and what is returned ("metadata and the OTP, not the body"). The explicit note that the body is not returned implicitly distinguishes it from get_message, so an agent can route correctly without opening the schema.

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 phrase "optionally only those sent to one address" signals when the filter is relevant, which is implied usage guidance. However, it never names siblings such as get_message or get_latest_otp or states when to prefer this list over them, leaving the agent to infer the boundary.

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