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

Annotations already declare readOnlyHint=true and the description reinforces 'READ-ONLY: it proposes, never settles', but it goes well beyond: the one-use-per-bill constraint, FX conversion at the line's own date rate, the 2% threshold, deterministic tie-breaking order, and the cross-currency-needs-fx failure mode from settle_bills. This is unusually rich behavioral disclosure.

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?

Dense but front-loaded: it leads with the core pairing action and constraint, then matching rules, then return shape and workflow. Every sentence conveys distinct information, though the volume is high enough that it reads as packed rather than lean.

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?

For a complex matching tool with no output schema, the description fully compensates by enumerating the return fields inline (pairs, settle_batches, unmatched_*, totals, truncated, limit), explaining `tied`, and describing the downstream settle flow. An agent has everything needed to call and interpret 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?

Schema description coverage is 100%, so the schema already documents supplier, from and to. The description restates the supplier format (sup-…) and due-date range but adds no syntax or meaning the schema lacks. Baseline 3 when the schema does the heavy lifting.

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+resource+scope: 'Pair ONE supplier's open bills to bank payments as a set, in one read-only call'. This clearly distinguishes it from siblings like match_transactions and settle_bills, and the one-to-one constraint is spelled out.

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?

Gives explicit when-to-use (pair open bills against money-out bank lines for one supplier), the workflow after calling (show pairs, then send each settle_batches entry to settle_bills), and the edge case (tied=true means ask the user). Alternatives and follow-ups are named directly.

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