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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety and determinism are covered. The description adds that the result is 'exact' and 'simplified' and produces multiple display forms, which is modest added context. It doesn't disclose error behavior (e.g., what happens for non-terminating non-repeating input), but with annotations covering the safety profile a 3 is appropriate.

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 front-loaded sentence that names the conversion and the outputs with no filler. Appropriately sized for a one-parameter utility, though it could have used a second short sentence to route among siblings without bloat.

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?

An output schema exists, so return values (fraction, mixed number, decimal display) need no elaboration, and annotations cover the safety/idempotency profile. The only meaningful omission is guidance on invalid or ambiguous input and on sibling selection, which keeps it just short of fully complete.

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%, and the schema itself richly documents the notation (0.125, 0.(3), 0.1(6), bars, and the '...' convention) with an example. The description only echoes the accepted input category, adding no syntax or format detail beyond the schema. Baseline 3 applies when the schema carries the parameter documentation.

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 (converts) and precisely scopes the resource: a 'terminating or explicitly repeating decimal'. It also names the three output forms (exact simplified fraction, mixed number, decimal display). It does not explicitly contrast with siblings like fraction_calculator or round_decimal, but the input/output scoping makes the tool's role clear.

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?

Usage is only implied through the input description ('terminating or explicitly repeating decimal'). There is no explicit when-to-use, when-not-to-use, or named alternative (e.g., fraction_calculator for fraction arithmetic, round_decimal for rounding). An agent must infer the boundary.

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