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

With no annotations, the description carries the full burden and does well: it states the action is irreversible, returns a deleted confirmation, and discloses the token cost. This covers key behavioral traits, though it could mention error handling or side effects, but those are less critical for a delete operation.

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 tight: action, prerequisite, targeting, irreversibility/return, and cost—all in four short lines. No filler or repeated information; every sentence earns its place.

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 simplicity of the tool (2 params, 100% schema coverage, output schema present), the description covers everything essential: the operation, prerequisite, instance targeting, irreversibility, and cost. Return values are handled by the output schema, so no further detail is needed.

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%, so a baseline of 3 is appropriate. The description repeats the instance selection logic that the schema already documents, adding no substantial new parameter meaning. The extra guidance about calling get_connected_accounts is more of a usage guideline than parameter semantics.

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 opens with 'Delete a Clerk phone number by id', a specific verb and resource that clearly distinguishes it from the many other delete_* tools in the sibling list. There is no ambiguity about what this tool does.

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?

It gives a clear prerequisite, 'Call clerk.get_connected_accounts first', and explains how to target a specific instance or default account with clerk_instance_id. It does not explicitly mention when not to use it or name alternatives, but the usage context is well established.

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