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

Annotations already include readOnlyHint=true, so the read-only nature is covered. The description adds valuable non-obvious behavioral detail beyond the annotations: it reports what the opponent would play, and it explains that a losing move may not appear in the top candidates, so direct probing with `considering` is needed. This is meaningful behavioral disclosure without contradicting the annotations.

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?

The description is front-loaded with the core purpose and then builds with high-value details about input formats, opponent replies, and the `considering` parameter. Every sentence adds distinct information, and there is no filler or repetition of the title or schema.

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?

Given there is no output schema, the description compensates by enumerating the return contents: engine evaluation, candidate moves with scores, side to move, check status, undefended pieces and attackers, material balance, and opponent's best reply. It also covers all input variants and the special `considering` behavior, making the tool effectively callable without missing critical information.

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 100%, so the baseline is 3. The description adds extra semantics for the `considering` parameter by explaining what it returns ('what that move actually walks into') and why it is necessary, which goes beyond the schema's one-line description. It also clarifies the input formats (FEN, PGN, or SAN moves from the start), reinforcing the schema.

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?

The description states a specific outcome: 'Returns an engine evaluation of a chess position' and enumerates the concrete contents — candidate moves, scores, check facts, material balance. This clearly differentiates it from siblings like chess_attacks and chess_review by focusing on engine evaluation rather than raw attack detection or review.

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?

The description gives useful contextual usage guidance, such as 'Pass considering with a move you are thinking of playing' and 'the difference between a position being quiet and merely looking quiet.' However, it never explicitly says when to choose this tool over chess_attacks or chess_review, nor does it mention any alternative or exclusion conditions.

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