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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, so the safety profile is covered. The description adds the per-project grouping of the result, which is genuinely beyond the annotations, but repeats the 'local date, default today' semantics already in the schema and says nothing about rounding, zero-hour days, or timezone edge cases.

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?

A single front-loaded sentence with no wasted words: scope first, then the per-project breakdown. Nothing is buried or redundant for its length.

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 one optional parameter, full schema coverage, and rich annotations, this is nearly complete; the description carries the extra burden of hinting at the return shape ('total hours ... per project') because no output schema exists. Only the numeric unit and empty-day behavior are left unspecified.

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 'date' parameter is already fully documented in the schema, including the YYYY-MM-DD format and the today default. The description restates the same default without adding format, boundary, or timezone meaning beyond it, 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 gives a specific verb+resource: total hours logged for one calendar day, broken down per project. The phrase 'one calendar day' implicitly separates it from summary_week and summary_client, though it never names those siblings 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 – an agent can infer this is the daily-aggregate counterpart to entry_list or summary_week, but the description states no when-to-use, when-not-to-use, or alternative-selection guidance.

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