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

With no annotations, the description carries the full burden of behavioral disclosure using 'Your call history' and 'what each call cost,' which clarifies the basic read nature. However, it does not explain ordering, limit behavior, scope of 'your,' or any cost/currency formats, leaving several behavioral implications undocumented.

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, focused sentence with no redundant words and delivers the main idea immediately. It is appropriately sized for a simple listing tool and 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?

The tool is simple, but with no annotations and no output schema, the description must explain enough to invoke it correctly. It does not clarify how caller and limit are used, what fields a receipt contains, or how results are ordered, so an agent still has significant ambiguity before calling 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?

The input schema provides only the names 'caller' and 'limit' with types, and the description does not explicitly define either parameter. 'Call history' weakly implies caller filters identity, and limit likely caps the number of receipts, but this is not stated, so the description adds minimal parameter meaning beyond the schema.

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 resource (call history through the router) and the key output (per-call cost), which is specific and not a tautology. However, it lacks an explicit verb like 'list' or 'retrieve' and does not directly distinguish itself from related financial or reporting siblings such as wallet_statement or list_paid_endpoints.

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?

There is no guidance about when call_receipts should be used instead of other tools. It does not mention alternatives, prerequisites, or likely use cases beyond the implied need for call history and costs, so the agent must infer context from the tool name and siblings.

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