lookup_us_routing_number

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

With no annotations, the description carries the full burden and largely meets it: it discloses that the call is metered against API credits, that a failed call must not be auto-retried, and that results are registry evidence which does not prove account existence or current ACH/Fedwire eligibility. It omits error shapes and what a False confirm_api_credit actually does, but the critical cost and reliability traits are disclosed.

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?

Four short sentences, front-loaded with the core action and followed by cost, formatting, and reliability constraints; there is essentially no filler. The telegraphic phrasing of the caveat sentence is slightly clipped but still parses cleanly.

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?

Operational constraints are well covered, but with no output schema and no annotations the description never says what a successful lookup returns (bank name, address, Fedwire status?), which matters for a tool whose siblings include lookup_bank. An agent knows the cost and the caveats but not the shape of the payload.

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 0%, so the description must supply parameter meaning, and it does: routing_number is constrained to 9 digits with a leading-zero preservation warning, and confirm_api_credit is framed as a credit-approval gate the user must authorize first. Neither parameter's behavior is restated from the schema because the schema documents nothing.

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?

Names a specific verb and resource (look up a 9-digit US routing number), from which an agent can infer it returns registry data for a routing number. It does not differentiate itself from the close siblings validate_us_routing_numbers or lookup_bank, so an agent must guess which of the three to call.

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 concrete pre-call workflow (obtain user approval for one API credit before setting confirm_api_credit=True) and a post-failure rule (do not automatically retry a metered call). It stops short of naming when to prefer validate_us_routing_numbers or lookup_bank instead, so routing between near-identical siblings is left to inference.

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