set_phone_number_block_list

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

No annotations are provided, so the description must fully disclose behavioral traits. It states that the tool replaces the block list (destructive), but does not mention authentication requirements, rate limits, validation of numbers, or error conditions. This leaves significant gaps for an agent.

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 very concise: three short paragraphs with no unnecessary information. The purpose is front-loaded in the first sentence, followed by a brief behavioral note, then parameter details. 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?

Given that an output schema exists (though not shown), the description provides essential semantics for a simple setter tool. However, it lacks information about side effects, validation, or error handling. It is adequate but not thorough.

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?

The input schema has zero description coverage, but the description's Args section adds clear meaning: phone_number_id is the ID from list_phone_numbers, and numbers are E.164 format with an example. This compensates well for the schema's lack of descriptions.

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 explicitly states the action: 'Set the block list for a phone number' and clarifies that these numbers are rejected. It also explains that it replaces the existing list. This clearly distinguishes it from related sibling tools like set_phone_number_allow_list.

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 notes that it replaces the existing block list and that passing an empty list clears it. It also mentions that phone_number_id comes from list_phone_numbers. However, it does not explicitly compare to alternatives like set_phone_number_allow_list, though the name makes the distinction clear.

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