get_phone_number

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

No annotations are provided, so the description carries the full burden. It states the tool retrieves data (a read operation) and describes the return format, which adds value. However, it lacks details on error handling, authentication needs, rate limits, or whether the operation is idempotent, leaving behavioral gaps for a tool with no annotation support.

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 front-loaded with the core purpose ('Get a phone number by ID'), followed by structured sections for arguments and returns. Every sentence is necessary and contributes to understanding, with zero wasted words, making it highly efficient and well-organized.

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's low complexity (single parameter, no output schema, no annotations), the description is mostly complete: it explains the purpose, parameter, and return format. However, it could improve by addressing potential errors or behavioral nuances, slightly reducing completeness for a tool with no structured safety hints.

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%, with the parameter 'id' documented as 'Phone number ID as string' in both the schema and description. The description adds no extra semantic meaning beyond what the schema provides, such as format examples or constraints, so it meets the baseline for high schema coverage without enhancement.

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 specific action ('Get') and resource ('phone number by ID'), distinguishing it from sibling tools like 'list_phone_numbers' (which retrieves multiple numbers) and 'update_phone_number' (which modifies a number). It precisely defines the tool's scope as retrieving a single entity by identifier.

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 usage context by specifying 'by ID', suggesting it should be used when you have a specific phone number identifier rather than browsing or filtering. However, it does not explicitly state when not to use it (e.g., vs. 'list_phone_numbers' for multiple numbers) or name alternatives, keeping it from a perfect score.

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