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

Annotations already flag this as a destructive, non-read-only op. The description adds real behavioral context the annotations can't: patch semantics (unsent fields are untouched) and that `values` merges rather than replaces. It stops short of stating reversibility or failure modes for a destructive write.

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?

Three short sentences, front-loaded with the core operation before the mutation semantics and the caution. No filler.

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 so return values need no explanation, and the partial-update/merge model plus the confirmation caution cover the main risks of a destructive patch tool. It omits cross-tool routing guidance against log_entry and any note on side effects such as reordering when occurredAt changes.

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 coverage is 100%, so the baseline is 3, but the description adds an undocumented merge rule specific to `values` that materially changes how an agent should populate it. That is genuine semantic value beyond the schema rather than restatement.

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+resource ('Corrects an entry') and immediately qualifies the update semantics ('Only the fields you send change'), which separates it from create-style siblings like log_entry. 'Corrects' is slightly idiosyncratic versus the title's 'Update', and no sibling is named, so it falls short of a 5.

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 implied: change an existing entry rather than logging a new one, and confirm unmentioned changes with the person. But it never says when to use update_entry instead of delete_entry plus log_entry, nor what prerequisites apply (ownership, entry existence). Guidance is present but incomplete.

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