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

Annotations already declare readOnlyHint=false, destructiveHint=false, and idempotentHint=true. The description adds valuable behavioral context beyond annotations: it discloses that ambiguous projects return candidates instead of logging, that it never auto-creates a project, and that it echoes parsed duration and resolved date for confirmation. It doesn't explicitly mention idempotency behavior, but the idempotency_key parameter description covers that. The description is consistent with annotations.

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?

The description is compact and front-loaded: it opens with the primary use case, then exclusions, then edge-case behavior. Every sentence earns its place, covering trigger conditions, exclusions, ambiguity handling, project creation policy, and confirmation behavior in just four sentences. No redundancy with 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?

For a tool with 10 parameters and no output schema, the description covers the key decision points: when to use, what to avoid, how to handle ambiguity, and what the tool echoes back. It doesn't describe the return format or error cases beyond ambiguity, but the schema covers parameter details and the description handles the main behavioral edge cases. The idempotency behavior is covered by the parameter description. A small gap is not explaining what happens when both duration and start/end are provided, but the duration parameter description covers that.

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 90%, so the schema already documents most parameters well. The description adds meaningful context beyond the schema: it explains the ambiguity behavior for the project parameter, clarifies that duration should be omitted when start/end are given, and notes that date should be omitted rather than guessed. These additions help the agent use parameters correctly without duplicating schema content.

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 ('log') and resource ('time entry'), and clearly distinguishes it from siblings by specifying the trigger condition: user states work done with a duration or start/end time. It also explicitly excludes future plans, reminders, timers, and calendar scheduling, which differentiates it from other tools.

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?

The description provides explicit when-to-use guidance ('when the user states work they did with a duration or a start and end time'), and explicit when-not-to-use guidance ('Do not use for future plans, reminders, timers, or calendar scheduling'). It also names the alternative behavior (returns candidates when project is ambiguous) and instructs the agent to ask the user and retry, plus a clear directive to never auto-create a project.

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