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

Beyond readOnlyHint=true, the description discloses refresh cadence (every 6 hours), the exact return shape, the confidence label semantics (HIGH/MED, LOW only for a labelled thin-market index with publication=thin_market), and what the surface deliberately withholds. This is substantial behavioral context an agent could not get from the annotations alone.

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?

Return shape and the core purpose are front-loaded, and most sentences earn their place. The closing clause about 'the anonymous surface does not enumerate the tiers or families it withholds' is somewhat abstract and could be tightened without losing meaning.

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?

With no output schema, the description usefully enumerates the returned fields and explains the two non-obvious ones (confidence, data_tier), which is exactly what is needed for a single-parameter read tool. Minor gaps remain: no guidance on behavior for an unknown slug or any rate/limit context, though these are low-value for a cached 6-hourly read.

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 description coverage is 100% and the slug's accepted forms (FLOPS-<MODEL>-OD/SPOT/DEPIN or bare gpu_model) are already documented in the schema. The description adds no further meaning about slug resolution, defaults, or behavior on an unmatched slug, so the schema carries the parameter entirely.

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 states a specific verb and resource: 'Fetch the current published value for a FLOPS compute price index.' It also implicitly separates itself from a richer sibling by noting it 'carries no methodology or source attribution by design,' but it never names get_index or list_indices, so sibling differentiation is only inferred.

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?

It gives a clear usage condition ('Cheapest way to answer what is the latest public reference price for X?') and signals the exclusion case by pointing out methodology and attribution are deliberately absent. It stops short of naming the alternative tool to use when methodology is needed, so the routing is suggestive rather than explicit.

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