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

Annotations already cover readOnly, idempotent, and non-destructive behavior. The description adds useful behavioral detail beyond that: it defaults to the current week in the workspace timezone, returns aggregates rather than entries, and explains that group_by 'day' renders a week grid.

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?

Four tightly written sentences, front-loaded with the primary use case, followed by the key distinction and defaults. Every sentence earns its place and there is no redundant restating of the title or 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 still covers purpose, aggregation behavior, default time window, grouping options, and the main sibling alternative. It falls slightly short on fully specifying date-range semantics and the exact aggregate fields returned, but it is largely complete for a read-only reporting tool.

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 only 20%, so the description must compensate. It gives meaning to group_by through 'hours by day, project, or client' and mentions the current-week default, but it does not explain how start_date and end_date define a custom range or exactly how client and project act as filters.

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 names specific use cases: hours worked, billable vs. non-billable split, hours by day/project/client, and unbilled amounts. It also distinguishes itself from time.list_entries by explicitly stating it returns aggregates, not individual entries.

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 opens with 'Use this when the user asks...' and explicitly routes individual-entry needs to time.list_entries. This gives both a clear trigger condition and an explicit alternative, leaving little to inference.

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