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

Annotations already declare readOnly/idempotent/openWorld=false, so the description's job is to add context — and it does: it discloses the 8-match cap, what fields come back (MARN, agency profile URL), and critically that this is a static copy of the OMARA register rather than a live check, with a required user-facing caveat. That data-freshness disclosure is behavioral information the annotations cannot convey.

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 sentences, front-loaded with purpose, then result shape and limit, then the caveat. No redundancy — each sentence adds a distinct fact an agent needs.

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 one-parameter read-only lookup with an output schema, the description covers purpose, result cardinality, returned fields, and the important limitation about register staleness. Nothing an agent needs to call or correctly represent the result 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 single parameter already documents both accepted forms with examples ('Jane Citizen', '1234567'). The description's 'by name or MARN' restates the schema without adding format handling, partial-match behavior, or ambiguity resolution rules, so it sits at the baseline.

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 and resource: checking whether a person is a currently registered migration agent by name or MARN, plus finding their agency. The person-focused scope implicitly differentiates it from the agency-oriented siblings, but the description never explicitly contrasts with search_migration_agencies or get_migration_agency, so the boundary is left to inference.

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?

'Use this to check whether a person appears as a currently registered migration agent' gives a clear triggering condition, and the closing instruction to point users to the OMARA register to confirm is actionable usage guidance. It stops short of naming when-not-to-use cases or naming a sibling as the alternative for agency-level lookups.

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