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

Annotations only supply destructiveHint=true and a title, so the description meaningfully adds PATCH-based partial-update semantics (unspecified fields are left untouched) and labels the operation WRITE. It still omits behaviors an agent would want for a mutation: permission requirements, whether approved/locked entries reject updates, and reversibility.

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 tightly packed segments: purpose and field list first, then the partial-update rule, then endpoint and write marker. No filler and the most decision-relevant information is front-loaded.

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 mutation tool with no output schema, the description covers scope, patch behavior, and the underlying endpoint, which is most of what an agent needs. Missing pieces are the update preconditions (locked/approved entries) and permission scope, so it is strong but not fully complete.

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 the schema already documents all 8 parameters with examples and constraints, which sets the baseline at 3. The description repeats a subset of the mutable field names and adds no format guidance (e.g., started_time/ended_time formats) beyond what the schema provides.

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 an existing time entry') plus the mutable fields (hours, notes, spent date, project/task), which clearly separates it from harvest_create_time_entry, harvest_delete_time_entry, and harvest_get_time_entry. It stops short of explicitly naming any sibling as the alternative, so it falls just under the top bar.

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: the patch semantics ('only the fields you provide are changed') tell the agent this is a partial edit of an existing record. However, there is no explicit when-to-use or when-not-to-use guidance, no mention of alternatives such as harvest_stop_time_entry / harvest_restart_time_entry for active timers, and no prerequisites.

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