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

No annotations are provided, so the description must disclose behavior. It does so by stating the max 24-hour limit and the 'ends now' behavior when startedAt is omitted. This adds meaningful context beyond the schema, though it doesn't cover authentication or return value.

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 concise sentences that front-load the purpose and then provide the key usage rules. No redundant information.

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 tool with 10 optional parameters, the description covers the critical usage patterns. The other parameters are well-described in the schema. The lack of an output schema means the agent doesn't need return details. The description is sufficient to invoke it correctly for typical cases.

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 covers all parameters at 100%, so baseline is 3. The description adds semantic value by explaining how duration, startedAt, and endedAt interact, and gives format examples for duration. This helps an agent construct valid calls.

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 clearly states the tool logs time already spent, gives a concrete example, and defines the primary parameters. It distinguishes from siblings by emphasizing 'already spent' vs. timer-based tools, though it doesn't name them 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?

It explains the two acceptable input patterns (duration alone, or startedAt+endedAt) and the behavior when startedAt is omitted. It doesn't explicitly compare to sibling tools like time_timer_start, but the phrasing 'already spent' implies it's for past time logging, providing enough context for selection.

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