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

No annotations provide safety hints, so the description carries the full burden. It discloses that the tool claims ownership of a number and triggers sending a text message (side effect), and explains the consequence for incoming texts. It doesn't discuss reversibility or auth, but the core behavior is clear.

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?

Two sentences, front-loaded with the purpose, and the second sentence compactly explains the procedure. No wasted words.

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 simple two-parameter schema, high schema coverage, and no output schema, the description adequately covers what the tool does and how to invoke it in both modes. It doesn't need to explain return values.

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 provides 100% coverage with descriptions for both number and code. The description adds context about the two-step flow but doesn't materially add meaning beyond the schema's own parameter 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 uses a specific verb 'Claim' and identifies the resource (a number) and its purpose ('so texts arriving from it reach this account'). It clearly distinguishes from sibling tools like sms_send by focusing on verification/claiming rather than sending or history.

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 explicitly describes the two-step usage flow: call with just the number to receive a code, then call again with the code. This provides clear context on how to use the tool, though it doesn't name alternative tools or exclusion scenarios.

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