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

Annotations declare readOnlyHint=false and destructiveHint=false, but the description adds meaningful behavioral context: the currency lock once expenses exist, the read-only nature of secure splits, and the requirement to open those in a browser. These go beyond what the annotations convey and give the agent actionable constraints.

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 sentences, all carrying meaningful information: what can be changed, the currency lock constraint, and the secure-split exclusion. 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?

The description covers the essential constraints (currency lock, secure split exclusion) and the tool is straightforward with a clear output schema. It's reasonably complete for a mutation of title/currency, though it could note whether title is optional or what happens with partial updates.

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?

With only 33% schema description coverage (only the 'split' param is described), the description partially compensates by explaining that title and currency are the two changeable fields and noting the currency lock constraint. However, it doesn't elaborate on title constraints or currency format beyond the schema enum. Given the low coverage, it could add a bit more but the basics are covered.

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?

Description clearly states the verb (change) and resource (a split's title or currency), and defines scope via the currency-locking constraint. It distinguishes from siblings by noting what kinds of splits it works on (simple, accountless) and which are excluded (secure splits).

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?

Explicitly states when it works (simple, accountless splits) and when it doesn't (secure splits must be opened in a browser). The currency-locking note implicitly guides agents away from attempting currency changes after expenses exist. However, it doesn't name specific alternative sibling tools for the excluded cases.

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