findfirst

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

With no annotations, the description carries the burden of behavioral disclosure. It explains input types, the return of the first matching item, the null fallback, and how to use 'this' for simple arrays. It could mention mutation (or non-mutation) and error handling, but the provided details are meaningful and not redundant.

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. Each sentence provides distinct information: input type, return behavior, and the 'this' keyword usage. It is appropriately sized and easy 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?

For a simple array-operation tool without annotations or an output schema, the description covers the essential behaviors: accepting arrays, matching conditions, returning first match, and the null case. It could give more details on condition syntax or object property handling, but it is sufficiently complete for basic invocation.

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 input schema has no parameters, but the description adds crucial semantics by explaining the condition and the propertyName keyword 'this'. This goes beyond the empty schema and aligns with the 0-param baseline of 4.

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 accepts an array and returns the first item matching a condition. The verb 'returns' and the resource 'array' are specific, and the 'first item' condition distinguishes it from siblings like filter, any, and every.

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 explains the core use case — finding the first matching element — and clarifies the no-match behavior (returns Null). It does not explicitly name alternatives or list exclusions, but the context is clear enough for an agent to decide when to use it.

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