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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered, but the description adds genuinely new behavior: prices and units are exactly as shown on the page (no normalization), a $0.002 USDC per-successful-call fee via x402 across Base/Solana/Arc, and that failed calls are not charged. That billing and unit-integrity disclosure is exactly the extra context annotations cannot carry.

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?

Two sentences: what it reads and what the rows contain first, then payment terms. No filler, and the most decision-relevant scoping constraint (one commodity, default gold, as-published units) is front-loaded before the commercial terms.

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 an output schema, 100% param coverage, and no required parameters, the description covers the important unknowns: units are not normalized, dates are monthly, and the call costs money. The only missing element an agent might want is expected latency/coverage of the underlying page, which is minor for a read-only table fetch.

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 both parameters are documented with range and slug examples, so the baseline is 3. The description adds one useful detail the schema omits: the commodity default is gold, which is a real gap-filler for a zero-required-parameter tool, but nothing beyond that.

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 verb+resource: reads an IndexMundi monthly commodity price table for one commodity (default gold) from the public commodity page, returning month and price as published. That is clearly distinguishable from any sibling, none of which cover IndexMundi commodity data. It stops short of explicitly naming an alternative for non-commodity price data, which keeps it from a 5.

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 only implied by the resource itself (monthly commodity price history); the description never says when to choose this over finance_world_bank, finance_alpha_vantage_public, or the many spot-price siblings. It does state a default (gold) and that months range up to 60 via the schema, but there are no exclusions or routing cues.

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