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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, open-world), so the description's main contribution is the fuzzy-match behavior: it accepts partial or misspelled names, which tells the agent it need not have an exact legal name. It also discloses the shape of the result (country, website, phone), which annotations do not.

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 sentences, no filler: the first defines the lookup and its return fields, the second gives the use cases. The most decision-relevant information (what it finds, what it returns) is front-loaded.

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 single-parameter, read-only lookup with no output schema, the description covers what is searched, how tolerant the matching is, what fields come back, and when to reach for it. Nothing an agent needs in order to call it correctly is missing.

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% and the schema already documents the name parameter with examples, so the baseline would be 3. The description adds a genuinely new semantic detail not in the schema: misspelled names are tolerated, which changes how the agent should construct the query rather than retrying with exact spellings.

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 gives a specific verb and resource ("Find card issuing banks by name") and immediately enumerates the returned fields (country, website, phone number). The sibling tools (lookup_bin, lookup_decline_code, lookup_mcc) each target a different lookup domain, so an agent can distinguish this one without opening any schema.

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?

It states two concrete use cases: confirming the bank behind a card and finding issuer contact details. It does not explicitly name when not to use it or point to a sibling (e.g., use lookup_bin when you only have the first digits), but the intended context is clear enough for correct selection.

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