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

Annotations already declare readOnly, openWorld, idempotent, and non-destructive behavior. The description adds critical context beyond annotations: it requires the user to connect their account, returns each carrier/service with price, currency, and transit days, and warns that prices are live and account-specific (do not cache). This covers auth needs, output shape, and a key operational constraint.

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?

Four sentences with zero waste: purpose and scope front-loaded, followed by return fields, auth/alternative routing, and caching caution. Every sentence contributes necessary information without redundancy.

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 9 parameters (6 required), no output schema, and rich annotations, the description is complete: it explains purpose, return values, auth requirements, caching behavior, and the alternative for unsigned users. The schema fully covers parameter semantics, so nothing critical is missing for correct 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?

Schema description coverage is 100%, so the schema already documents all 9 parameters with units and examples. The description adds only the phrase 'one parcel' and does not provide any parameter-level guidance beyond what the schema provides; baseline 3 is appropriate.

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?

States a specific verb (Compare) and resource (live shipping rates) for one parcel across every carrier on the signed-in account, and explicitly distinguishes it from get_shipping_quote for users without an account. The agent can tell exactly what the tool does and how it differs from the sibling.

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?

Explicitly says when to use (signed-in account, live account-specific prices) and when not to use (for someone without an account use get_shipping_quote, which needs no sign-in). It also adds a caching caution, leaving no ambiguity about context or alternatives.

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