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

Annotations already declare the tool as read-only, idempotent, non-destructive, and closed-world, so the description need not repeat these. The description adds a small behavioral insight: it returns 'one institution profile' (a single record lookup) and emphasizes 'exact' certificate number, implying no fuzzy matching. However, it does not go beyond that, so it only adds marginal value over the annotations.

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?

The description is two concise sentences with no filler. It front-loads the primary use case, then the alternative for discovery. Every word earns its place.

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 simple two-parameter read tool with an output schema and comprehensive annotations, the description fully covers what an agent needs: the exact input condition, the output nature (one profile), and how to find the cert if unknown. No significant gaps remain.

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%, with both parameters (cert, fields) already documented. The description reinforces that cert is the unique identifier and requires an 'exact' match, but it does not add new syntax or format details beyond the schema. Baseline 3 is appropriate since the schema carries the full burden.

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 clearly states the tool's function: 'Get Institution by Certificate Number' with a specific verb ('get') and resource ('institution profile'). It explicitly distinguishes from siblings by specifying the condition 'when the user knows an exact FDIC Certificate Number' and contrasts with search tools like fdic_search_institutions and fdic_search.

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 description provides explicit usage guidance: use when the user knows an exact CERT number and needs one profile. It also gives a direct alternative for discovery ('To discover a CERT first, call fdic_search_institutions or fdic_search'). This fully covers when-to-use and alternatives.

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