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 concrete API shape (GET /v3/grants/{grant_id}/events/{event_id}) and notes calendar_id is a query param, but says nothing about failure modes (e.g. missing event/calendar) or auth requirements.

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, front-loaded with the core action, followed by the required-param caveat and the raw endpoint. Nothing extraneous and no filler.

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 low-complexity fetch-one tool with full schema coverage and a readOnly annotation, the description supplies the action, the required param behavior, and the underlying endpoint path. The only gap is that with no output schema, it does not hint at what the returned event object contains.

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 all three parameters are already documented in the schema, including the 'sent as a query param' note. The description's restatement of calendar_id's query-param behavior duplicates rather than extends the schema, 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?

The description states a specific verb+resource ('Get a single calendar event by id'), and the word 'single' implicitly contrasts with the sibling nylas_list_events. It never names that sibling explicitly, so sibling differentiation is left to inference rather than stated.

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 context is only implied by 'by id' - the agent can infer this is the fetch-one operation rather than a list. There is no explicit when-to-use, no exclusions, and no pointer to nylas_list_events as the alternative for browsing.

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