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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds substantive context beyond them: results are computed by the rules alone, no engine evaluation happens server-side, and the Stockfish engine actually runs in the user's browser at the returned URLs. This is exactly the kind of behavioral disclosure that prevents an agent from misusing the tool as an evaluator.

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?

Front-loads the purpose and return values, then closes with the crucial scope limitation. It is a single dense paragraph that is somewhat long, but every sentence contributes information an agent needs.

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, yet the description still names the key facts returned and, more importantly, clarifies the division of labor between rule-based facts and browser-side engine analysis via the returned URLs. Nothing essential for correct invocation is missing.

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 coverage is 100%; the schema already documents that FEN is required and that move counters may be omitted. The description reinforces that the input is a FEN but adds no format or edge-case detail beyond the schema, so the baseline 3 applies.

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 (read/analyze) and resource (a chess position from FEN) and enumerates the exact facts returned: side to move, status, legal moves in SAN, material count, opening name. It is clearly distinguishable from siblings like identify_opening and analyze_game, which cover narrower or different scope.

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?

Explicitly bounds the tool with 'does not evaluate the position and does not choose a best move' and routes evaluation elsewhere via analysisUrl and bestMoveUrl. That is strong when-not guidance, though it never names the sibling tools themselves as alternatives.

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