list_unused_indexes

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

With no annotations, the description carries the full burden and does well: it discloses that usage data is 'best-effort', explains the YES/NO/UNKNOWN tri-state of likely_unused, and names the external dependency (ALTER INDEX ... MONITORING USAGE) needed for definitive answers. It does not explicitly state that this is a read-only operation, which is a minor remaining gap.

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?

Three tightly packed sentences: purpose first, then flag semantics, then the limitation. Every sentence earns its place and the most important caveat is placed alongside the flag it qualifies.

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 one-optional-parameter listing tool with no output schema, the description adequately covers what is returned (indexes, columns, usage info) and how to read the key flag. It could be slightly more complete about the monitoring requirement being per-connection or about result volume, but nothing essential to 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?

Schema description coverage is 100% for the single optional 'schema' parameter, including the 'omit rather than guess' guidance, so the schema already does the heavy lifting. The description adds no parameter-level detail beyond what the schema provides, making the baseline 3 correct.

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 precise verb and resource ('List indexes with their columns and best-effort usage information'), which is more specific than the sibling list_indexes by promising usage data. It does not explicitly name or contrast with list_indexes, so the differentiation must be inferred from the 'usage information' wording.

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 the tool's use case (assessing whether indexes are unused) and warns that definitive answers require DBA-run index monitoring, which is a real usage caveat. However, it never says when to pick this over list_indexes or other index-related siblings, leaving the routing decision implicit.

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