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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds the useful detail that this maps to GET /applicants/{applicant_id}, but says nothing about what happens on a missing/invalid id (error shape) or whether the response is cached. Adequate but thin for a read tool whose annotations already carry the main signal.

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 short sentences, zero filler, with the core action front-loaded before the API mapping. Every clause 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?

There is no output schema, so the description ideally would hint at what an applicant record contains (e.g., status, PII fields), and it does not. For a trivial get-by-id tool the gap is minor, but the description is thinner than the full burden requires when no output schema exists.

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?

Only one parameter, and schema coverage is 100% ('The applicant id.'), so the structured data already documents it fully. The description adds no format, source, or retrieval hint for the id beyond the name, 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 ('Retrieve') and resource ('a single applicant record by id'), and the word 'single' implicitly separates it from the sibling onfido_list_applicants. It stops short of naming competitors like onfido_get_check or onfido_get_report, but the resource is unambiguous.

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?

Usage is only implied: 'by id' suggests you must already hold an applicant id, which distinguishes it from the list/search-style siblings. No explicit when-to-use, prerequisites, or exclusion against onfido_get_check / onfido_get_workflow_run is given.

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