type

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

The description discloses that the return value is a string and that 'none' is returned when the key doesn't exist, which is a key behavioral trait. Without annotations, the description carries the transparency burden and adequately conveys it is a read-only operation. It does not explicitly state 'no side effects,' but the nature implies it.

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: one sentence of purpose, followed by an Args and Returns section. Every sentence is necessary, and the structure (docstring-like) is clear and front-loaded with the key information. No waste.

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 tool's simplicity (one parameter, no nested objects), the description fully covers its purpose, input, and output. The existence of an output schema is noted, but the description already states the return type and the special 'none' case. There is no missing information to use this tool correctly.

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 0% description coverage (only title and type). The description compensates by explaining that 'key' is the key to check, providing semantic meaning beyond the schema's minimal definition. It also indicates the return type and the 'none' case, adding value for parameter understanding.

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 returns the string representation of the type of the value stored at a key. It uses a specific verb ('Returns') and identifies the resource ('type of the value at key'). Among sibling tools like 'get' (returns value) or 'exists' (checks existence), 'type' is distinct and the description makes its purpose unambiguous.

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 states what the tool does but provides no explicit guidance on when to use it versus alternatives or when not to use it. While the purpose is clear, it lacks usage context like 'Use this to check the type of a key before performing type-specific operations.' The absence of when-not conditions or alternative mentions is a gap.

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