check_sim_swap

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It explains the output (a date) and the rationale (fraud signal), but it does not disclose behavior for invalid or unknown numbers, potential errors, or whether this is a read-only operation. For a simple lookup, this is adequate but not detailed.

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 two sentences, front-loaded with the primary purpose, and contains no filler. The second sentence adds practical usage context without bloat, making it an example of efficient writing.

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?

For a single-parameter lookup tool with no output schema, the description gives the core purpose and a use case, but it does not describe the return value's structure or edge cases (e.g., no swap ever, invalid number). This is minimally viable but leaves the agent to guess response details.

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 covers 100% of the parameter (phoneNumber) with 'Number to check.' The description does not add any extra meaning or format guidance (e.g., E.164 format), so it relies entirely on the schema. This meets the baseline but does not enrich parameter understanding.

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 ('Return') and a clear resource ('the date a number was last SIM-swapped'), and it distinguishes itself from sibling tools like check_age_on_network by focusing on SIM swap events. It also adds the fraud-signal context, making the purpose unmistakable.

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 provides explicit when-to-use guidance: 'check this before disbursing to an unfamiliar number.' This gives a clear operational context. However, it does not mention alternatives or when not to use the tool, keeping it just below the highest bar.

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