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

With annotations already declaring a non-read-only, non-destructive mutation, the description still earns credit for real behavioral detail: patch-only semantics, the start/end invariant enforced when minutes is supplied, and the fact that tags REPLACES rather than appends. The tags-replacement warning matters because destructiveHint=false could otherwise lead an agent to assume additive merging. Missing is what the response contains and whether task/project values must already exist.

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?

A single dense sentence that front-loads the core action and then enumerates the four non-obvious semantics in priority order. No filler, no restatement of the title, and nothing an agent must skim past to reach the important clauses.

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 an 11-parameter partial-update mutation with no output schema and only partial schema descriptions, the description covers the highest-risk unknowns (list replacement, duration vs. end interaction, rate units, validation refusal). Remaining gaps are the return shape and referential constraints on task/project, which are secondary for correct invocation.

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 only 55% across 11 parameters, so the description has to compensate and largely does: it explains that minutes is a duration that moves end while pinning start, that rate is hourly in major units, and that tags is a full overwrite. note, task, project, billable and currency remain undocumented in either place.

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?

"Change one logged entry by id" gives a specific verb (change), a specific resource (a single logged entry), and an addressing key (id). The clause "only the fields you pass move" immediately separates it from entry_add/entry_log (create) and entry_delete, so an agent can pick the right sibling without opening a 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?

Usage is implied rather than stated: editing presumes an existing entry whose id came from entry_list, and the tool is implicitly for corrections after logging. There is no explicit when-not guidance (e.g. use entry_mark_billed for billing state, entry_delete for removal) and no stated prerequisites or permission requirements.

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