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

Annotations already mark readOnlyHint=true, and the description adds meaningful behavioral detail: unoccupied squares return an empty list, output includes piece type and colour, and the accepted position formats are disclosed. No contradiction with the read-only annotation exists.

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?

Two tightly written sentences front-load the core result and the key edge case, then list accepted input formats. Every sentence earns its place and there is no filler or redundant restatement of the tool name.

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?

The description is complete for a simple computation tool: it explains the return value and the empty-list case, which is especially important because there is no output schema. It names all three position input types, though it does not specify what happens if multiple position arguments are supplied or what the default starting position is.

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%, so the baseline is 3. The description adds context by naming FEN, PGN, and SAN moves as the position inputs and noting that SAN moves begin from the starting position. However, 'square' semantics are left to the schema's example, and the description does not significantly deepen parameter understanding.

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 opens with a specific verb—'Returns the exact list of squares attacked'—and names the resource: the piece standing on a given square. It also includes return details (piece type and colour) and edge-case behavior, making its purpose unmistakable and distinct from the broader chess_analyse and chess_review siblings.

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 implies usage: use this when you need the squares a particular piece attacks. It also states the accepted input formats (FEN, PGN, or SAN moves), which helps with input preparation. However, it never explicitly compares this tool to chess_analyse or chess_review, nor gives when-not-to-use guidance.

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