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

With no annotations, the description carries the full behavioral burden and does disclose the key traits: it is free, requires no payment and presents no x402 challenge, and is a direct GET-equivalent read of a static criteria document. It stops short of stating response shape or whether the criteria are versioned/cached, which is a modest remaining gap for an unannotated tool.

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?

Purpose is front-loaded in the first sentence, followed by the access/cost note and the HTTP equivalent. The dash-fragment formatting ('- no payment required:') is slightly awkward and the phrase 'rules every paid answer is reproducible from' is dense, but no sentence is wasted.

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-parameter, read-only criteria endpoint with no output schema, the description covers what it returns, that it costs nothing, and its HTTP equivalent — enough for correct invocation. The missing piece is how it relates to query_index_lookup and query_index_precheck in the workflow.

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 to disambiguate and the baseline of 4 applies. The description correctly signals a parameterless direct call rather than leaving the agent to wonder about required inputs.

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 specific resource: the published criteria for the Query Index service (agent-query-index/v1), including the reproducibility rules and the pinned public test corpus identity. It is clear what the tool returns, but it never distinguishes itself from the sibling tools query_index_lookup and query_index_precheck, which share the same namespace.

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 only implied: an agent can infer it should read the criteria before or alongside query_index_lookup. The one explicit instruction is procedural (call directly, no payment needed), but there is no when-to-use/when-not guidance and no routing to the sibling lookup or precheck tools.

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