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

Annotations already declare a safe read (readOnlyHint=true, destructiveHint=false, openWorldHint=false), and the description adds real context beyond them: rate limits (shared 10 calls/day, 1 MCP trial call/day), per-call cost, and the important disclosure that the aci series is SUSPENDED per ADR 0006 with existing prints retained but no new prints. That suspension note is exactly the kind of behavioral trait annotations cannot express.

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?

The opening rhetorical question ('Is today's number a real move or ordinary noise?') is marketing framing rather than information, and pricing details precede the actual content. The metric list and the aci caveat are valuable, but the piece is not tightly front-loaded.

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 no-output-schema read tool with fully documented parameters, the description covers cost, rate limits, metric semantics, and a suspended-series caveat well. The main gap is that one enum value (settled_share_by_service) is absent from the metric list, leaving a slight mismatch with the 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 description coverage is 100%, so the baseline is 3. The description adds meaning for the aci metric's suspension and clarifies the series is not market data, but it omits settled_share_by_service even though the schema enum contains it, and says nothing about days/from/to semantics that the schema doesn't already cover.

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 — returning Paddock's own first-party chart series by metric and date range — and enumerates the available metrics. It also draws a boundary against non-siblings ('this is Paddock's series, not token prices'), though it doesn't distinguish itself from close siblings like get_liveness or get_market_summary.

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 context is implied through pricing tiers (free pk_free_ key, x402 at $0.01/call, MCP-only free trial) rather than stated as when-to-use guidance. There is no explicit statement of when to pick this tool over the sibling series tools, so the agent must infer the choice.

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