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

Annotations already indicate this is a write operation (readOnlyHint=false) and not destructive. The description adds valuable context beyond that: partial payments lower the chased amount, full payments close the ladder and free the free-tier slot, and it returns the outstanding amount. This goes beyond the annotations and helps the agent understand side effects.

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 two sentences with no filler. It front-loads the action, then explains the two possible effects and the return value. Every phrase earns its place, and it is appropriately sized for the tool's complexity.

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 description covers the purpose, the effects on the invoice ladder, and the return value. It does not need to explain parameters because the schema handles that. It could mention prerequisites or error cases, but for a straightforward payment-recording tool, this is sufficiently complete.

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 the schema already documents all parameters clearly. The description reinforces that amount_minor is in 'whole MINOR units', which matches the schema, but it does not add new semantic meaning that isn't already present. Baseline 3 is appropriate when the schema carries the parameter documentation.

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 specific verb ('Record money received') and a specific resource ('against a chased invoice'), clearly distinguishing it from sibling tools like invoice_status (querying) and overdue_list (listing). It also explains the two possible outcomes (partial vs. full payment), making the tool's intent unambiguous.

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 clear context: it is used for payments against a chased invoice. It does not explicitly mention when not to use it or name alternative tools, but the context is sufficient for an agent to infer the appropriate scenario. No exclusions are given, so it falls short of a 5.

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