Update Expense

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

With no annotations, the description carries the full disclosure burden. It goes beyond a generic 'update' by stating that unspecified fields are left untouched and that supplying users overwrites the entire shares mapping – a non-obvious destructive edge case. It doesn't cover permissions or side effects, but the most safety-relevant behaviors are disclosed.

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 sentences with no filler. The primary verb phrase is front-loaded, and the critical edge case about users overwriting shares is isolated at the end for emphasis.

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?

Despite the output schema and concise core semantics, the tool has 10 parameters and no annotations. The description leaves most parameter behavior, required identifiers beyond expense_id, and side effects undocumented, so an agent would still have to guess meaning for fields like repeat_interval or currency_code.

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 0%, so the description must add parameter-level meaning. It only explains the 'users' parameter's overwrite behavior; the other nine parameters (cost, date, details, group_id, category_id, description, currency_code, repeat_interval) are left to inference from their names and types.

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 opens with a specific verb and object – 'Update an existing expense' – clearly identifying this as the mutation tool for an existing expense. The word 'existing' distinguishes it from create_expense, delete_expense, and get_expense without needing to inspect the 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?

The phrase 'Update an existing expense' implies when to use it: when an expense already exists and needs modification, not creation or deletion. However, it does not explicitly name alternatives, prerequisites, or exclusions such as when restore_expense or delete_expense would be more appropriate.

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