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

With no annotations, the description carries the full burden of behavioral disclosure. It only states it generates placeholder phone numbers, but does not explain the behavior of the 'format' parameter (us vs. international), the output format, or any constraints beyond what the schema provides. Minimal transparency.

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 description is a single concise sentence that efficiently communicates the core purpose. It is front-loaded with the verb and resource. However, it could include more detail without becoming verbose.

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?

Given the tool has an output schema and only two parameters, the description is adequate but incomplete. It does not mention the default count or format, nor does it clarify that the output is an array of phone numbers. The presence of an output schema partially compensates, but the description could be more complete.

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 baseline is 3. The description adds no additional meaning beyond the schema for the parameters 'count' and 'format'. It does not clarify the difference between 'us' and 'international' formats or the nature of the placeholder output.

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 the tool generates random placeholder phone numbers. However, it does not distinguish from the sibling tool 'random_phone', which also generates random phone numbers. The description lacks specificity about batch generation vs. single generation.

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 guidance is provided on when to use this tool over alternatives like 'random_phone', 'validate_phone', or 'format_phone'. There is no when-to-use, when-not-to-use, or mention of context.

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