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

Goes well beyond the readOnly/openWorld annotations by disclosing the commercial model: $0.002 USDC per successful call via x402 across Base, Solana or Arc, with failed calls not charged. That cost/authorization context is exactly the kind of information an agent needs before invoking a paid 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?

Four compact clauses, front-loaded with what the data is and its units, followed by scope limits and pricing. No filler sentences; each clause adds a distinct fact.

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?

An output schema and annotations already exist, so the description needn't explain return structure. It still covers source provenance, units, coverage limits, and payment terms, leaving nothing material an agent needs before calling.

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 'days' parameter already documents range and default, so the schema carries the load. The description's 'up to 60 trading days' adds mild clarification of the trading-day semantics but is largely redundant with the schema.

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?

States a specific resource (Henry Hub natural gas spot price) with units (USD per MMBtu), source (FRED/EIA series), and returned scope (latest value plus up to 60 trading days). This clearly separates it from siblings such as energy_ttf_european_gas or energy_crude_oil_brent_wti.

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?

Explicitly states what the source does not cover ('Pipeline storage and LNG netback are not included'), which steers an agent away from misuse. It does not, however, name an alternative tool for those adjacent data needs, so routing is only partially handled.

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