Find duplicate expenses

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

Annotations already mark this as read-only, idempotent, and non-destructive; the description reinforces this with 'Read-only: nothing is changed or deleted' and adds useful behavioral context about the matching criteria and the returned 'clusters with a confidence and a suggested action.' No contradiction exists between the description and annotations.

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 is three sentences with no filler: purpose and criteria, output shape, and safety guarantee. Each sentence earns its place, and the key 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 moderately complex read-only scan tool, the description provides the detection criteria, output summary, and a clear safety statement, while the schema and output schema cover parameter details and return structure. It is slightly incomplete in not offering alternative routing or a more precise definition of 'similar words,' but nothing essential for calling it is missing.

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?

The schema documents threshold and since_days with defaults and ranges, covering 67% of parameters; group_id is not described but is self-evident from context. The description adds algorithm-level context but does not explain how threshold or since_days affect the duplicate scan beyond what the schema already states.

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 states a specific verb ('Scan'), a resource ('a group for expenses'), and a precise goal ('look like duplicates'), backed by concrete criteria: same amount, currency, payer, time window, and similar words. This clearly differentiates it from the sibling find_missing_expenses, which targets missing rather than duplicate entries.

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 intended use is implied: call this when you want to detect likely duplicate expenses within a group. However, the description does not explicitly state when to prefer it over alternatives such as find_missing_expenses, nor does it give exclusions or when-not-to-use guidance.

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