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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely non-derivable behavior: the decision is rule-based rather than a model's opinion, and the response carries reason codes, requested fields, evidence and a signature, plus a reference to the equivalent HTTP endpoint.

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?

Three tight sentences, with the core purpose and the enumeration of return states front-loaded so the agent reads the important part first. The endpoint URL is marginally useful but slightly noise.

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 compensates by listing the four decision outcomes and the accompanying artifacts (reason codes, fields to request, evidence, signature). The deterministic rule-based nature is also disclosed. Only minor gaps remain, such as error or not-found behavior.

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 each of the five fields is already documented in the schema. The description restates the optionality of payer, amount and purpose and the sid meaning without adding format or validation detail beyond the schema, so the baseline 3 applies.

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 ('the receiving side's check before settlement') and clearly frames which side of the transaction it decides for, which separates it from the payer-side siblings like payment_decision and check_payment_request. It even enumerates the possible outcomes the tool produces.

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 phrase 'before settlement' establishes the timing context and 'receiving side' establishes the role, so an agent knows when to reach for it. It does not, however, explicitly name a sibling alternative or state a when-not condition, which keeps it below a 5.

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