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

Annotations declare a non-read-only, non-destructive, non-idempotent mutation, and the description adds real context beyond them: the default applies only to future entries, re-rating re-stamps existing entries, and the return value includes a count of changed entries. It does not mention permissions or whether overwritten rates are recoverable, which matters for a re-stamping operation.

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 tight sentences with the core action front-loaded and the return value second. No filler or redundancy.

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?

With no output schema, the description usefully states what is returned (new rate and, conditionally, the count of changed entries). Combined with fully documented parameters, an agent has enough to call it correctly, though the interaction between apply_to_existing and only_missing could be spelled out more.

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 schema already documents all five parameters in detail, including currency defaults and rate parsing. The description only reinforces the apply_to_existing behavior and the returned change count, adding little beyond the structured fields.

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?

The description gives a specific verb and resource ('Set the hourly rate and currency') plus the business effect ('turn tracked hours into money for a project or client'). It is clearly distinct from siblings like target_set or entry_edit, though it never names an alternative explicitly.

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 only implied: 'when re-rating is asked for' hints at apply_to_existing, and the default of future-entries-only is stated. There is no explicit when-to-use/when-not guidance or routing to entry_edit for per-entry rate changes.

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