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

Adds substantial context beyond the annotations: explicit pricing ($0.01 per call), the payment rail (USDC on Solana via x402), the two-step 402-challenge handshake, and the equivalent HTTP endpoint. This explains why readOnlyHint=false on an apparently read-only query. It does not disclose response shape or whether counts are rolling-window, which is a remaining 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?

Three sentences, front-loaded with the data purpose, followed by the payment mechanics and HTTP equivalent — each sentence carries non-redundant information. The x402 sentence is dense but only as long as it needs to be to make the two-call flow actionable.

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 one-parameter tool with no output schema, the description covers what an agent most needs to call it correctly: cost, payment handshake, and the alternate HTTP path. Missing only the return-value semantics (what the counts look like, rolling vs. fixed window), which matters more without an output schema.

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 coverage is 100% and the single optional 'hub' parameter is fully documented in the schema as an HB_* filter defaulting to all seven hubs. The description adds no parameter-level meaning beyond that, so the baseline of 3 applies.

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 precisely — ERCOT negative-price windows with 24h/7d counts — which distinguishes it by domain qualifier from its power_flags_* siblings (battery, congestion, dart) and power_scan. The verb is implicit ('returns counts') rather than stated, but an agent can tell what data it yields without opening the schema.

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?

The sentence about calling without payment first to receive the PaymentRequired challenge, then retrying, is genuinely useful procedural guidance for invocation. However, there is no guidance on when to choose this tool over power_flags_congestion/battery/dart or power_scan, and no mention of the hub filter's role in selecting it. Usage is implied by the domain label only.

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