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

Annotations already declare readOnly, idempotent, non-destructive and openWorld=false, so the safety profile is covered. The description adds useful provenance (ASPCA 2021 national averages) that signals these are rough US national estimates, but it says nothing about the shape of the result, and the 'per month' trigger is not backed by any stated monthly output.

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, no filler, with the purpose and the data source front-loaded and the usage trigger second. Every sentence earns its place.

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 simple, zero-required-parameter, purely computational tool with no output schema, the description gives enough to call it correctly: what it computes, on what basis, and when to reach for it. Only the return structure and the all-defaults (0 pets) edge case are unaddressed.

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 coverage is 100% and every parameter carries its own description and default, so the schema does the heavy lifting. The description only loosely gestures at the parameters ('first-year costs' hints at include_one_time) without adding format or behavior detail beyond the schema.

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 ('Estimate') and resource ('yearly and first-year costs of dogs and cats') plus the data provenance (ASPCA 2021 national averages). It is implicitly distinct from siblings like dog_years_calculator, though it doesn't name any sibling explicitly.

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?

'Use when someone asks what a pet costs per year or month' gives a clear triggering context, which is more than most tools offer. It stops short of exclusions or naming an alternative tool when the question is about something else (e.g. lifespan or weight).

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