index_stats

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

readOnlyHint=true already declares the safety profile, and the '[READ]' prefix merely restates it. It adds the return-content description (column lists, cardinality) which is useful since there is no output schema, but discloses nothing about auth, cost, or limits.

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 compact overall. The '[READ]' marker is wasted tokens given readOnlyHint=true, but the size is well matched to a single-parameter tool.

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-parameter read-only tool, the description covers what it returns and how to target it. With no output schema it usefully sketches the return shape, leaving only minor gaps around scope or filters.

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 0%, so the description carries the burden, and it does explain the lone parameter: 'Target name from config; omit for the default.' That clarifies the meaning and default behavior beyond the bare string 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?

States the resource clearly ('Per-index column lists and cardinality') and gives a purpose ('selectivity screening'). An agent can distinguish it from sibling index tools like unused_indexes and redundant_indexes, though it never names a sibling explicitly.

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 parenthetical '(selectivity screening)' implies the diagnostic context for using this tool, but there is no explicit when-to-use, when-not, or routing to alternatives such as unused_indexes or redundant_indexes.

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