number_fact

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered externally. The description adds nothing beyond that – no note on external API dependency, failure behavior, or what happens when no fact exists for a number.

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?

A single tight sentence with the core action front-loaded and zero filler. It is efficient, though the brevity is part of why semantics are thin.

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?

A simple 2-parameter read-only tool with rich annotations and no output schema needs only modest description, and this covers the basic action. It is still incomplete regarding the meaning of the 'type' modes and the default behavior, which an agent needs to pick a mode 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?

Schema coverage is only 50%: the 'number' parameter has no description at all, and the 'type' enum is documented only by repeating its own values. The description does not compensate – it never explains what trivia/math/date/year mean or which is the default, leaving the key semantic gap unaddressed.

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?

States a specific verb and resource ('Get an interesting fact about a number'), which distinguishes it from siblings like number_random, is_even, or prime_check. It stops short of explaining what kinds of facts are available, but the core purpose is unmistakable.

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 versus alternatives such as number_random or the math-function siblings, and no mention of how the four 'type' modes change the answer. The agent must infer usage entirely.

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