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

Annotations already declare readOnlyHint=true and idempotentHint=true; the description adds meaningful behavior beyond that: it accounts for provider tiered pricing and prompt-cache price, and sorts offers by estimated cost ascending. These details tell the agent what factors influence results and output ordering.

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 tight sentences, front-loaded with the core purpose and scoping (one model, per provider), then key behaviors and sorting. Every clause earns its place; no filler or repetition of schema details.

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?

Without an output schema, the description adequately explains the return values: offers with cost per request and per-month cost (if requests_per_day is given). It could clarify what happens when token counts are omitted, but overall the tool's behavior is sufficiently complete for an agent to call and interpret it.

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 all six parameters already have clear meanings. The description adds some linking context (requests_per_day triggers monthly cost; prompt-cache price affects cached_ratio), but it does not substantially extend the schema's parameter documentation. 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 action (estimate cost) on a specific resource (a workload on one model at each provider), and details the calculation: per-request and per-month cost, tiered pricing, prompt-cache price, and cheapest-first sorting. This clearly distinguishes it from siblings like price_history or search_models.

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 gives a clear context: estimating workload costs with optional token and request-volume inputs. It does not explicitly name alternatives or exclusions, but the sibling names differ enough (cheapest, compare_providers, price_history) that an agent can infer when estimate_cost is appropriate.

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