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

Annotations already declare readOnlyHint, destructiveHint false, and openWorldHint, so the safety profile is covered. The description adds non-annotation context that matters operationally: the zero-filled empty-cell convention, that solutions are gated behind paid plans, and a 4-credit cost per call.

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?

Three short sentences, front-loaded with the core capability followed by output convention and cost. The opening redundantly repeats the tool title before the verb, a small waste, but otherwise nothing extraneous.

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-format explanation is unnecessary, and cost/paid-tier behavior is covered. However, for a single-parameter tool the description leaves the valid difficulty values unspecified, which is the one thing an agent needs to invoke it 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?

Only one parameter and schema description coverage is 100%, so the schema already documents 'difficulty'. The phrase 'across multiple difficulty settings' confirms the axis but never enumerates accepted values, and the schema has no enum, so the description fails to compensate for that specific gap.

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 concrete verb+resource: 'creates 9x9 Sudoku puzzle grids', and adds distinguishing detail such as zeros for empty cells and solution grids on paid plans. It doesn't explicitly differentiate from neighbors like CrosswordGenerator or WordSearchGenerator, but the resource itself is 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?

Usage is implied by the resource (generate a Sudoku puzzle) and it adds a useful commercial condition: the solution grid requires a paid plan and each call costs 4 credits. There is no explicit when-to-use vs alternative statement, but the sibling set contains no direct Sudoku competitor requiring routing.

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