splitwise_update_expense

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It discloses a key behavior: providing a users array overwrites all existing shares. However, it does not mention other important aspects such as idempotency, authorization requirements, or what the tool returns. Given the expected update behavior, the description is adequate but not comprehensive.

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?

The description consists of two concise sentences with no redundancy. The first sentence states the primary purpose, and the second provides critical usage guidance. Every word earns its place, making it highly efficient for an AI agent to parse.

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?

Given the moderate complexity (10 parameters, all documented in schema) and no output schema, the description covers the most important behavioral aspects. It lacks explanation about return values, but since no output schema exists, this is a minor gap. The guidance on partial updates and users array overwrite is valuable. Overall, the description is complete enough for an agent to use correctly.

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 baseline is 3. The description adds practical value beyond the schema by explaining usage patterns: 'Only include fields that are changing' and the specific behavior of the users array. This helps the agent decide which parameters to include and understand side effects.

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 clearly states the tool's purpose: 'Update an existing expense.' It distinguishes from sibling tools like splitwise_create_expense and splitwise_delete_expense by focusing on modification. Further nuance is added with guidance on updating partial fields and the behavior of the users array.

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?

The description provides clear context: use this tool to update an existing expense. It advises to 'only include fields that are changing' and warns about overwriting shares when providing users array. While it doesn't explicitly list when not to use or alternatives, the sibling tools offer obvious alternatives (create, delete) and the guidance is sufficient for an update tool.

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