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

Annotations already cover the safety profile (readOnlyHint, destructiveHint=false, openWorldHint), and the description adds genuinely new behavioral context: the error semantics and the fact that results describe existing registrations rather than availability. It stops short of disclosing pagination, result caps, or matching behavior (exact vs partial), which are the remaining unknowns.

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?

Three tight sentences, front-loaded with the purpose and followed by the alternative routing and the error caveat — every sentence carries information. The enumerated return-field list is somewhat redundant given an output schema exists, which is the only inefficiency.

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 two-parameter read tool with full annotation coverage and an output schema, the description covers purpose, sibling routing, caller expectations about errors, and output shape. Nothing an agent needs in order to select and 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 enum for entity_type is fully documented in the schema, so the structured data carries most of the load. The description restates that query accepts a name or RC/BN number but adds no matching semantics or guidance on when to narrow by entity_type, so baseline 3 applies.

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 (search), a specific resource (CAC public register for businesses registered in Nigeria), and the two lookup keys (name or RC/BN number). It also explicitly positions itself against the availability-check siblings, so an agent can distinguish it 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?

Explicitly says what this tool is not and names the two alternatives that perform availability checks (check_name_availability, check_business_name_compliance). It also gives a usage rule for the error case ('An `error` never means there's no match'), removing a common misinterpretation.

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