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

With no annotations, the description carries the behavioral burden. 'Counts' implies a read-only operation and 'last crawl' adds freshness context, but it does not explicitly mention side effects, authentication needs, or failure behavior. It adds some value without being fully transparent.

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 extremely concise, using a single colon-delimited phrase to list the key statistics. Every word contributes meaning, and the most important term 'Truthful counts' is front-loaded.

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 no-parameter statistics tool, the description is reasonably complete: it names the specific data points returned. The absence of an output schema is compensated by these listed categories, though it does not explain whether values are live or cached beyond the 'last crawl' hint.

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?

The tool has zero parameters and full schema coverage, so there is no parameter information needed beyond what the schema already provides. The description appropriately focuses on the output categories rather than parameters.

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 identifies the tool as providing counts of indexed records, live endpoints, observations, and last crawl. The title and description align, and the index-specific focus differentiates it from the sibling tools, though it lacks an explicit verb like 'retrieve' or 'return'.

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?

No guidance is given about when to use this tool instead of siblings such as check_status or list_capabilities. The reader must infer that index_stats is for metrics about the index, but the description does not explicitly state exclusions or alternatives.

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