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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds two non-trivial behaviors not present in structured fields: the required OAuth scope and the exact upstream route, and it hints at the returned data (time spent coding). It stops short of describing response shape or error 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?

Three short sentences with zero filler: purpose first, auth prerequisite second, endpoint last. Every sentence contributes distinct information and nothing is repeated from the schema.

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?

With no output schema, the description carries some burden for return values and does note the time-spent data, though not its fields. Combined with full schema coverage, annotations covering the safety profile, and the explicit scope requirement, an agent has enough to call this correctly; only the response structure is thin.

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 hash, branch and project semantics (formats, defaults, source of values) are already fully documented in the schema. The description adds no parameter-level detail beyond naming the hash, so the 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 and resource ('One commit of a WakaTime project by hash') plus the payload it returns ('the time spent coding on it'), which cleanly separates it from the sibling wakatime_list_commits. An agent can identify the tool without opening the schema.

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?

It gives a real prerequisite ('Needs the read_heartbeats scope for OAuth tokens') and pins the underlying endpoint, which is useful context for invocation. However, it never states when to reach for this versus wakatime_list_commits; the alternative is only implied through the schema's hash description, so the routing guidance is incomplete.

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