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

Annotations already declare readOnly, idempotent, and non-destructive. The description adds useful behavioral detail beyond those: exact price vs min/max range, no accuracy percentage promise, free/no key requirement, and ~100ms latency. This is exactly the kind of supplementary context annotations do not carry.

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 front-loaded with the core return behavior, then uses compact sections for examples, when to use/not use, cost, and latency. Each part earns its place and there is no filler or tautology.

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?

There is no output schema, so the description carries the burden of explaining return values. It covers cost, latency, success probability, fixed vs range behavior, and the important caveat to check `cost_range`. It also addresses caching, authentication requirements, and latency, making it complete for an estimation 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 coverage is 50%, so the description must compensate. It does so with concrete invocation examples showing `operation` and `params` shapes, and it clarifies that `params` mirrors the actual operation request body. The description does not enumerate valid operation values, but the examples and context provide enough for correct use.

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 uses a specific verb ('Return') and names the exact resource: cost, latency, and success-probability estimates for a proposed call. It also distinguishes fixed vs range outcomes, making it clear this is a pre-execution estimator rather than an actual execution or status tool.

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?

Explicit sections say when to use it ('under a budget constraint... before proceeding') and when not to use it ('do not use in a hot loop... cache for at least 60 seconds'). This gives an agent actionable routing and exclusion guidance with no inference required.

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