update_time_entry

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

Annotations already declare destructiveHint=true, idempotentHint=true and openWorldHint=true, so the safety profile is covered. The description adds genuine non-schema behavior — end_time is derived read-only from start_time + hours — but never mentions the destructive nature, that changes are irreversible, or how the confirm-preview flow gates the mutation (only the schema's own field description covers that).

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?

Front-loads the purpose in one line, then spends the rest on format semantics that the schema lacks — no filler sentences. The line breaks mid-sentence are slightly awkward but the ordering is logical.

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 destructive 9-parameter mutation with 11% schema coverage and no output schema, the description should do more: it should say whether this is a partial update, what happens to fields not supplied, and what the confirm=false response looks like. It covers only the hours/start_time arithmetic.

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 11% across 9 parameters, so the description must compensate — and it does for the two most error-prone fields: hours is an ISO8601 duration ('PT8H', 'P1D') and start_time is an ISO8601 date-time. However, seven other parameters (user, comment, ongoing, activity, spent_on, time_entry_id) get no treatment, and it doesn't say whether omitted fields are left unchanged or cleared.

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?

States a specific verb and resource ('Update a time entry') and explicitly distinguishes itself from the sibling update_time_entry_until by explaining that end_time cannot be passed here. An agent can select between the two update tools without opening either schema.

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?

Names a concrete alternative and the condition selecting it: use update_time_entry_until when you have an end time instead of hours. That is real routing guidance. It stops short of stating prerequisites (e.g., whether the entry must be owned by or visible to the caller).

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