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

Annotations already declare readOnlyHint/idempotent/destructive=false, so safety is covered. The description usefully adds the degradation profile: rich content for 18 openings, name/ECO/moves only for the rest, and a found=false fallback with suggestions.

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-loaded with the purpose and input formats, then progressively adds output content and edge-case behavior. Dense but every sentence carries information; not padded.

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?

For a single-parameter read tool with an output schema and full annotation coverage, this describes return contents, coverage limits, the no-match path, and outbound links. Nothing an agent needs to invoke it correctly 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?

Schema coverage is 100% and the single parameter already carries examples, so the schema does the heavy lifting. The description's examples add marginal reinforcement but no new format or syntax rules beyond what the schema provides.

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 (look up) and resource (a chess opening guide), and clarifies the input key (name or slug) with concrete examples. It is readily distinguishable from siblings like identify_opening and analyze_position.

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?

Explains what kinds of inputs resolve to full guides (18 popular openings) versus partial catalog entries (~3,700 names), and what happens on no match (found=false, suggestions). It does not explicitly contrast with identify_opening, which is the natural alternative when only a position is known.

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