retell_update_phone_number

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 says 'update' which implies mutation, but it doesn't mention potential side effects, reversibility, permission requirements, or what happens when unsetting agent IDs. The behavior of passing empty strings is left to the schema, not described.

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 sentence that is front-loaded with the verb and resource, and it conveys the core purpose without unnecessary words. It could be slightly more detailed, but it is concise and to the point.

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?

This is a simple update tool with 4 well-documented parameters and no output schema. The description is sufficient for basic understanding, but given no annotations and no output schema, it would benefit from a mention of return behavior or success/failure indicators. It is minimally complete but has gaps.

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 the schema fully explains each parameter. The description itself adds no additional parameter semantics beyond what the schema provides. Baseline 3 is appropriate when schema does the heavy lifting.

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 updates agent binding or settings for an existing phone number, using the specific verb 'update' and identifying the resource ('existing phone number'). It distinguishes from sibling tools like retell_create_phone_number and retell_delete_phone_number by focusing on modifying existing numbers.

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 (when updating an existing phone number's settings), but it does not explicitly state alternatives or exclusions. For example, it doesn't mention that creating a phone number should use retell_create_phone_number. Usage is implied rather than explicit.

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