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

readOnlyHint=true already declares this is a safe, non-mutating read, so the description does not need to establish that. It adds the underlying REST mapping (GET /v3/grants/{grant_id}), which is minor context, but says nothing about auth scope requirements, what fields are returned, or error/not-found behavior.

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 no filler, and the purpose is front-loaded ahead of the API mapping. The endpoint line adds marginal value for an agent that already has a typed tool interface, but it is not wasteful enough to penalize much.

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 single-parameter read tool with a full-coverage parameter schema, readOnly annotations, and no output schema to explain, the description covers what is needed to call it correctly. Only the lack of routing guidance toward nylas_list_grants keeps it from being fully complete.

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% and the single grant_id parameter is already documented in the schema, including the NYLAS_GRANT_ID override behavior. The description only echoes {grant_id} via the endpoint path, adding no semantics beyond the schema, so the baseline 3 is 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?

States a specific verb and resource ('Get details for a single connected account') and disambiguates the Nylas jargon 'grant' by equating it with 'connected account'. The word 'single' implicitly distinguishes it from nylas_list_grants, though that sibling is not named explicitly.

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: 'a single ... grant' suggests fetching one known grant versus listing all, but there is no explicit when-to-use, no prerequisites, and no named alternative (e.g. nylas_list_grants) to route the agent. Adequate but with a clear gap.

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