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

Annotations already declare readOnlyHint=true, covering the safety profile. The description adds the REST endpoint mapping, which usefully shows grant-scoped path access, but it omits error behavior (e.g., not-found handling), auth requirements, and response shape. That is adequate but not rich.

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 with the core action front-loaded and no filler. The endpoint reference is compact and earns its place for API-oriented agents.

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 single-record read with full schema coverage and readOnly annotations, the definition gives enough to invoke correctly. It does not describe the returned contact object, but no output schema exists and that omission is minor.

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%, so both parameters are already documented in the schema. The endpoint string in the description echoes that grant_id and contact_id are path parameters but adds no syntax or format detail beyond the structured fields, making the baseline 3 appropriate.

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 states a specific verb and resource ('Get a single contact by id') and scopes it to one record, which implicitly contrasts with the sibling nylas_list_contacts. It stops short of explicitly naming the list alternative, so it is clear but not maximally differentiated.

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 implied: call this when you have a contact_id and need the full record. There is no explicit when-to-use vs when-not, no mention of the list_contacts alternative, and no prerequisites such as required scopes or valid grant context.

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