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

Annotations already establish that this is a safe, read-only, idempotent, closed-world lookup. The description adds meaningful behavior beyond that by listing the guide contents and explaining that non-exact names return matching ECO lines.

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 compact and front-loaded, with the main content stated first and the fallback behavior second. The long first sentence is dense but every clause describes useful returned content.

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 simple one-parameter lookup with annotations and no output schema, the description is largely complete: it covers what the guide contains and how non-exact names are handled. It could be stronger with explicit sibling routing, but no critical invocation detail 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%, so the name parameter is already well documented with examples. The description adds value by clarifying that other names trigger a list of matching ECO lines, which is behavior beyond the schema's parameter description.

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 clearly states the resource and the specific content returned: first moves, ECO codes, play frequency, scoring, main lines, and ideas. It is distinguishable as a name-based opening guide, though it does not explicitly contrast itself with siblings such as identify_opening.

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?

Usage is implied: look up an opening by name to get a guide. The fallback behavior for other names is useful, but there is no explicit when-to-use or when-not-to-use guidance versus alternatives like identify_opening or analyze_position.

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