I

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

No annotations are provided, so the description fully bears the burden of behavioral disclosure. It clearly identifies the tool as a read-only getter with no side effects, returning a constant value. The return value is explicitly documented (I = sqrt(-1)), and the example confirms the output.

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: only 3 short sentences plus an example. Every word serves a purpose (purpose, return value, example). No redundant information. It is front-loaded with the key action 'Get the imaginary unit'.

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 (no parameters, constant return), the description is complete. It explains what the tool does, what it returns, and shows usage. The presence of an output schema (implied by context) further reduces need for return details, but the description already covers it.

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 parameters, schema coverage is trivially 100%. The description adds no parameter info because there are none. However, it does explain the return value and provides an example, which is valuable context. According to guidelines, 0 params baseline is 4, but the description goes beyond by explaining the output, earning a 5.

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 explicitly states 'Get the imaginary unit', which is a clear and specific verb+resource. The name 'I' is ambiguous alone, but the description resolves it perfectly. It distinguishes from siblings (e.g., 'complex', other constants) by being the simplest constant for sqrt(-1).

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?

While no explicit alternatives or when-not-to-use are given, the tool's purpose is self-evident (a mathematical constant). Sibling tools like 'complex' could construct complex numbers, but for retrieving the imaginary unit itself, this is the only option. The simplicity makes explicit guidance unnecessary.

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