check_sim_swap

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

With no annotations, the description carries full weight. It discloses the output (swapped bool, timestamp, carrier), live carrier data source, and pricing ($0.25 per check). It does not mention rate limits or authentication, but for a simple check tool this provides adequate behavioral context.

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 three sentences, each serving a clear purpose: core functionality, usage guidance, and pricing. No filler; front-loaded with the most critical information.

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 tool with one parameter and no output schema, the description covers all essential aspects: purpose, usage context, return values, time window, data source, and cost. It is self-contained and leaves no significant 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?

The single parameter 'phone' is fully described in the schema (E.164 format, pattern). The description adds no extra parameter-specific meaning beyond mentioning Twilio Lookup v2; thus baseline 3 is appropriate given 100% schema coverage.

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 detects SIM swap or eSIM provisioning events on a phone number within the last 24 hours. It uses a specific verb ('detect') and resource, and distinguishes itself from sibling tools like check_breach or check_domain_lookalikes by focusing on carrier events.

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?

Explicit guidance is given: use when a user reports losing mobile service or before high-risk actions depending on SMS authentication. While no exclusions are stated, the context is clear and siblings are sufficiently different, making ambiguity low.

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