List Parcel Carriers

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

Annotations already declare the tool safe (readOnly, non-destructive, idempotent). The description adds behavioral context beyond that: the data is 'daily-updated' (so results change over time) and 'requires no API key' (auth simplicity). It also cites the exact GET endpoint, providing transparency about what operation is performed.

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 primary purpose, no filler. Every word earns its place: purpose, update frequency, scope, endpoint, and auth requirement are all covered efficiently.

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 (one optional param, no output schema), the description is complete. It explains the return value (map of codes to names), the data freshness, the endpoint, and auth requirements. Annotations cover safety, so there are no significant missing details for selection and invocation.

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 has one optional parameter (response_format) with an enum and default, which is self-explanatory. The description does not mention this parameter, but the schema already conveys its meaning. While schema description coverage is 0%, the simple enum-based param does not require additional explanation, so the description adds no specific parameter semantics but does not create a gap.

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 'Return the complete, daily-updated map of Parcel carrier codes to names,' which is a specific verb+resource with scope. It also distinguishes from siblings like find_carriers by emphasizing completeness and daily updates, and names the endpoint, leaving no ambiguity about what it 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?

The description provides clear context—this returns a complete, daily-updated mapping and requires no API key—so an agent knows when to use it for a full list. It does not explicitly exclude alternatives like find_carriers, but the scope is well-defined, giving sufficient guidance without needing explicit exclusions.

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