What this agent has paid, and whether it settled

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

readOnlyHint already tells the agent this is a safe read, so the bar is lower. The description still adds meaningful context beyond the annotation: it discloses that receipts include denied decisions, not just allowed ones, and that a reconciliation step distinguishes settled from outstanding payments. It does not describe truncation or pagination behavior tied to the limit parameter.

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 sentences, no filler, with the core scope (receipts plus reconciliation) front-loaded and the action-oriented use case trailing. Every clause carries information.

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?

With no output schema, the description usefully summarizes the return payload (payment decisions plus settlement reconciliation), and annotations cover safety. Both parameters are schema-documented. Only minor gaps remain, such as how results are ordered or capped.

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 both 'limit' and 'window' are already documented in the schema; baseline is 3. The description's mention of outstanding payments hints at the reconciliation window concept but adds no format or default detail 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 states a concrete verb and resource: it returns this session's Rein receipts (every payment decision, allowed or not) plus reconciliation of which allowed payments settled. That is far more specific than the title alone. It does not explicitly differentiate itself from siblings like rein_status or rein_fetch, so it stops short of a 5.

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?

It gives a clear use case: 'Use it to check whether a payment really went through.' That is real guidance for selection. However, it names no alternatives or when-not-to-use conditions relative to rein_status, rein_escalations, or rein_fetch.

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