acos

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

Annotations already declare readOnlyHint=true and idempotentHint=true, indicating a safe, deterministic operation. The description adds valuable behavioral context by specifying that the result is in degrees by default and can be changed to radians via the unit parameter. No contradictions with 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 extremely concise, consisting of two short sentences. Every word serves a purpose, with no redundancy or fluff.

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 mathematical function with clear purpose and two parameters, the description combined with the schema provides sufficient information for an AI agent to use the tool correctly. The output is straightforward, so no output schema is needed.

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?

With 0% schema description coverage, the description must compensate for parameter details. It explains the unit parameter and its default, but does not explain that 'value' is the cosine input (implicit from context). The description adds marginal value beyond the schema for the unit parameter, but leaves the 'value' parameter undescribed.

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 'Arccosine' which clearly identifies the mathematical function, and specifies default unit (degrees) and the option for radians. However, it does not differentiate from sibling functions like asin or atan, missing a chance to clarify when to use arccosine specifically.

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?

There is no guidance on when to use this tool versus other trigonometric functions. The description only defines what it does, with no mention of prerequisites, context, or alternatives.

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