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

No annotations are provided, so the description carries the burden. It does disclose a meaningful side effect ('store anything new'), signaling this is not a pure read, which is valuable. However it says nothing about permissions, idempotency/duplicate handling, rate limits, or pagination.

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?

One sentence, front-loaded with the fetch action and ending with the return behavior. No filler; every clause carries information.

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?

No output schema exists, so the description must cover the return value, and it does ('return every message'), plus it flags the persistence side effect. Missing only details like message shape, ordering, or limits for a full picture.

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% for the single numberId parameter, so the schema already documents it. The description's phrase 'of a virtual number' loosely maps to numberId but adds no format, ID-source, or validation detail beyond the schema.

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?

Specific verb+resource with scope: fetches a virtual number's inbox, persists new messages, returns all messages. This distinguishes it from read-only siblings like check_sms or get_virtual_number, though it never names a sibling explicitly.

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?

No when-to-use, when-not-to-use, or alternative named. The agent must infer that this is the tool for retrieving messages for a given number id, and cannot tell from the text how it differs from check_sms.

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