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

Annotations already mark readOnlyHint=true, and the description adds substantial behavior beyond that: it promises factual information only, disclaims hints/coaching, enumerates exactly what will be returned, and states every response includes a solve_url. This is rich behavioral context for an agent.

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?

Four sentences with no wasted text: the main purpose is front-loaded, followed by return behavior, the key exclusion/alternative, and a stable response-field guarantee. Every sentence contributes useful information for tool selection or invocation.

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?

There is no output schema, but the description compensates by enumerating the return facts (completeness, correct cells, incorrect cells with entered digit, empty count) and the guaranteed solve_url. It also gives concrete user utterances for when to call it, so an agent has all the information needed 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?

Schema description coverage is 100%, and both parameters (puzzle and progress) are already documented as 81-character strings with empty-cell conventions. The description does not need to re-explain parameters, so it stays at the baseline 3 because the schema carries that burden.

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 object: "Check a user's current progress against the correct solution." It further enumerates the exact factual outputs (completeness, correctness, incorrect cells, empty count) and explicitly contrasts with the sibling explain_next_step by saying it does not give hints or coaching, so an agent can distinguish it without opening schemas.

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?

Gives explicit trigger phrases: "Use this when the user asks 'am I done?' or 'did I make any mistakes?'" and names the alternative for hint requests: "Does not give hints or coaching — use explain_next_step for that." This covers both when to use and when not to use the tool.

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