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

The annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. Against that lower bar the description adds genuine value by spelling out the return structure — one row per capability threshold with price, cost-decline multiple, and halving time — which matters because no output schema exists. It does not say how fresh the index is or whether it is a fixed published artifact or recomputed on each call, which is the main remaining behavioral 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?

One front-loaded sentence introduces the index and then lists its fields in a parallel structure that is easy to parse. It is dense but every clause carries content; only the nested parenthetical about blended USD pricing verges on over-compression.

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?

A zero-argument read tool with no output schema places the burden of describing returns entirely on the description, and it meets that burden by naming all three per-threshold values plus the unit basis. What is missing is metadata an agent would want before calling: data recency and the source of 'first-party API price'. That is a modest gap rather than a blocking one.

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?

With zero parameters there is nothing to disambiguate, so the baseline of 4 applies. The description does not waste words re-describing an empty schema, which is appropriate.

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 a specific artifact — a 'cost-of-intelligence index' — and enumerates the three quantities it reports per GPQA Diamond threshold: cheapest first-party blended API price in USD per million tokens, the improvement multiple, and the months-to-halve figure. That is specific enough to distinguish it from the news-oriented siblings (daily/weekly/monthly/story/search). It stops short of an explicit verb or a direct contrast with any sibling, so it is clear but not fully differentiated.

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 guidance on when to reach for this index versus eacc_get_latest, eacc_get_monthly, or eacc_search. The description is a noun phrase describing the payload, not an instruction, so an agent must infer that this is the tool for AI-price-versus-capability analysis. No exclusions, preconditions, or alternative routing are offered.

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