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

Beyond the annotations (readOnlyHint=false, idempotentHint=false), the description discloses substantial behavior: the entry lands in DRAFT status, duplicates on (task, date) are rejected, the timeTracking feature (PRO+) is required, and the caller must be a project member or org admin. Only minor gaps remain (no failure/error behavior, no return shape).

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?

It is front-loaded with verb+resource and every sentence carries a distinct constraint (range, format, status, duplicates, feature gate, permissions). It is slightly dense and run-on, but nothing is wasted.

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 mutation tool with full schema coverage, rich annotations, and no output schema, the description supplies the missing operational context: creation state, duplicate handling, feature tier, and authorization requirements. An agent has everything needed to call it correctly.

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 the schema already documents every parameter, including the hours range and date format the description repeats. The one genuine addition is the (task, date) uniqueness constraint, which is more behavioral than parameter semantics, so the baseline of 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 and resource ('Log hours against a task as a timesheet entry') and clarifies ownership ('Records under the calling user, on the specified task within the specified project'). It is clear on its own, but it never distinguishes itself from the sibling create_timesheet_entry, which an agent could easily confuse it with.

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 real conditions: entries start in DRAFT and 'submission for approval is a separate operation', and duplicate (task, date) entries are rejected so the caller should edit the existing entry instead. That routes the agent away from re-creating, but it does not explicitly name the alternative tools or when to prefer create_timesheet_entry over this one.

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