np_arccos

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

No annotations are provided, and the description does not disclose behavioral traits such as domain restrictions (e.g., NaN for out-of-range values), output units (radians), or error handling. The parameter schema mentions the input range, but the description itself lacks transparency.

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 extremely concise with only two phrases. It is front-loaded with the core operation and avoids any unnecessary words, making it efficient for quick parsing.

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 simplicity of the tool and the presence of an output schema (assumed), the description covers the essential functionality and element-wise nature. The domain constraint is handled in the parameter description, so the main description is adequately complete for a basic math operation.

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 100% with the parameter description clarifying the allowed input range. The tool description adds no additional parameter information beyond what the schema provides, meeting the baseline for high coverage.

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 'Inverse cosine, element-wise' clearly states the mathematical operation (inverse cosine) applied element-wise to the array. It distinguishes from sibling functions like np_arcsin and np_arctan by specifying the specific trigonometric inverse.

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 does not provide any guidance on when to use this tool versus alternatives. It only states the function without contextual recommendations or restrictions beyond the parameter schema.

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