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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description adds real behavioral detail beyond that: results are ranked with reasons and trade-offs, and excluded entries are returned with explanations — non-obvious output behavior worth disclosing.

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 dense sentences with the core differentiator front-loaded and no filler. The long filter enumeration is justified since it defines scope, though it is slightly list-heavy.

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 an output schema present, the description needn't explain return values, yet it helpfully notes reasons, trade-offs, and exclusions. Combined with 100% schema coverage and rich annotations, an agent has everything needed to invoke it correctly; only the missing sibling reference keeps it from a 5.

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% with self-documenting enums, so the baseline is 3. The description goes further by explaining the weighting consequence of a parameter — 'sub-cent amounts weight settlement cost heavily' — which maps typical_amount_usd to an observable effect the schema does not convey.

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 (choose/recommend) and resource (HTTP 402 payment rail) and explicitly frames it as requirements-driven rather than rank-driven, which distinguishes it from get_best_payment_solution. It also enumerates the filter dimensions and the re-weighting behavior, so an agent knows exactly what the tool computes.

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 'from requirements rather than from rank' clearly signals when to pick this over a ranking-based sibling, and the filter list implies the context of use. However, it never names the alternative tool explicitly, so the routing guidance is clear but not fully prescriptive.

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