index_info

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

No annotations are supplied, so the description carries the disclosure burden; it does at least tell the agent the response is aggregate/coverage metadata rather than documents themselves, which sets expectations for a side-effect-free lookup. It does not state that the call is read-only, cheap, or that it takes no arguments and always succeeds, so the behavioral picture is only partial.

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?

It is extremely short with zero padding and front-loads the useful content, but it is a sentence fragment missing a subject/verb, which reads as a truncated docstring rather than a complete definition.

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 zero-argument, read-only tool with an output schema, the description covers the essentials of what comes back. What is missing is orientation relative to search/outline/fetch — the agent has no cue about when this summary call is the right choice — which is the main gap given the tool's simplicity.

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 takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The enumerated items are response fields rather than inputs, and an output schema already exists to define them.

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 names the resource ('this index') and enumerates what it reports (sources, document counts, date ranges, version tag counts), which is enough to infer a metadata/summary tool distinct from search, outline and fetch. But it is a noun-phrase fragment with no verb – it never says it 'returns' or 'reports' anything, leaving the agent to infer the action.

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?

There is no when-to-use guidance at all: nothing says whether to call this before searching, to check coverage, to verify a date range is populated, or how it relates to the sibling tools search/outline/fetch. The implied use (inspect corpus coverage) is left entirely to inference.

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