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

Annotations already declare readOnlyHint=false, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds a genuine behavioral trait not present in annotations: partial-update semantics where omitted fields are preserved. It stops short of describing failure behavior for invalid ids or field conflicts.

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 short sentences, zero waste, with the action front-loaded and the patch-semantics caveat immediately after. Nothing superfluous and nothing buried.

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?

An output schema exists and annotations cover the safety and idempotency profile, so the description needn't explain return values. It is nearly complete for a partial-update tool, missing only notes on validation failures or the minutes/duration exclusivity that would help prevent a malformed call.

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 each of the six parameters is already documented, including the id source ('from list_entries'), date format, note max length, and the minutes/duration exclusivity. The description only re-lists a subset of fields, adding no syntax or constraint detail beyond the schema, so the 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?

States a specific verb ('Change') and resource ('an entry') and enumerates the mutable fields (project, date, minutes, note), so the agent knows exactly what the tool operates on. It does not, however, distinguish itself from nearby siblings like merge_entries, delete_entry, or log_time.

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 clause 'Only the fields you pass change' implies patch-style editing of an existing entry, which is useful invocation guidance. But it never says when to prefer this over merge_entries, delete_entry, or log_time, so usage is only implied rather than directed.

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