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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, so the safety profile is covered. The description adds valuable context: values are null if no official source exists, and prices are never invented. It also states 'Paid per call,' which is a behavioral trait not in annotations.

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?

Three sentences with no waste. The core purpose is front-loaded, the source credibility is stated, and the null behavior is disclosed. 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 read-only lookup tool with 100% schema coverage and no output schema, the description covers the essential behavior: what it returns, the source, the null policy, and the cost model. It doesn't describe the exact response structure, but that's acceptable given no output schema and the simplicity of the tool.

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 four parameters. The description adds the meaning of tokens_in/tokens_out as 'to price a call' and clarifies the output format (USD per 1M tokens), but doesn't add much beyond the schema. 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?

The description clearly states the tool is an LLM price oracle that returns official input/output USD per 1M tokens for a provider:model plus estimated call cost. It distinguishes itself from siblings by specifying the exact resource (LLM pricing) and the source (verified price table).

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 implies when to use this tool: when you need official LLM pricing or call cost estimation. It doesn't explicitly name alternatives or exclusions, but the sibling list shows other paid_* tools with different purposes, so the context is clear enough.

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