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

With readOnlyHint/idempotentHint already declaring the safety profile, the description still adds real value: it is free (no additional charge), results expire after 60 minutes, and omitting the argument lists recent calls newest-first. It does not describe the response payload shape, though that is partly inferred from the title.

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?

Tight, front-loaded prose: what it does, when to use it, the costly mistake to avoid, then the invocation pattern and retention limit. Every sentence carries operative information with no filler.

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 single-optional-parameter read tool with no output schema, the description covers the call pattern, the listing fallback, the cost model, and the 60-minute retention window. Nothing an agent needs to invoke it correctly or decide between it and `call` is missing.

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%, so the baseline is 3, but the description adds ordering semantics ('newest first') and the purpose of the omitted-argument mode that the schema field description only gestures at. It clarifies intent rather than merely restating the property.

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 and resource ('get the response from a paid call you already made') and immediately separates itself from the sibling `call` by framing it as a post-hoc fetch. An agent can distinguish it from `call`, `quote`, `balance`, and `rate` without opening any schema.

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?

Explicitly names the trigger condition ('use it when `call` never returned'), explains the mechanism (client timeout while the call still completes and charges), and states the exclusion with a reason ('Do NOT repeat the `call`... that is a second charge'). Alternatives and non-usage are both covered.

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