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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds meaningful behavioral context beyond annotations: results are sourced, ordered cheapest first, include free-tier flags and signup links, and calls are paid per use. It also notes that the tool has no local context, which is valuable for an agent deciding on data dependencies.

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 a single, well-structured sentence that front-loads the core purpose ('LLM routing catalog') and then packs relevant details into the rest. Every clause adds information: input flexibility, output fields, pricing unit, sorting, public data scope, and cost. There is no redundant or filler content.

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 catalog tool with all optional parameters and complete schema coverage, the description provides sufficient context. It explains what the tool returns, the ordering, the data source, and the billing implication. Even without an output schema, an agent has enough to invoke the tool and interpret the result shape at a high level.

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 baseline is 3. The description adds useful semantic context beyond the schema by clarifying that results are sorted 'cheapest first' and that the price unit is USD per 1M tokens, which helps the agent interpret the budget parameter. It also maps the 'need' keyword and budget to the optional parameters in an intuitive way.

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 identifies the tool as an 'LLM routing catalog' and states that it returns provider:model options with prices, free-tier flags, and signup links. The verb 'returns' and resource are specific. It does not explicitly differentiate itself from the closely related sibling paid_model_price, though the catalog/routing framing implies a broader search role.

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 conveys when it is appropriate to call the tool: when you have a need keyword and/or budget and want provider:model options. It also clarifies that data is public and that calls are paid, which helps an agent decide whether to invoke it. However, it does not state when to choose an alternative like paid_model_price or provide explicit exclusions.

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