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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and openWorld, so safety is covered. The description adds genuinely useful behavior beyond that: the default Gulf producer set when countries is omitted, the reported:false handling of missing months and exclusion from ranking instead of zero-filling, and keyless access. Return format and pagination are not described.

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?

Front-loads the core comparison behavior, then supplies two concrete examples and the missing-month rule. It is dense and slightly repetitive ("both are the same comparison, just different country lists"), but every sentence carries actionable information.

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 carries the burden of the return shape and does partially: it says results are ranked by change and that missing countries are flagged reported:false. It does not describe the record structure (country, values, change magnitude/units), so an agent knows the gist but not the exact payload.

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's parameter content (months_back 3 = quarter-over-quarter, 12 = year-over-year, countries default set) largely restates what the schema already documents in its own property descriptions, adding little net meaning.

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 and resource — comparing JODI-Oil countries on one series, latest reported month vs N months earlier, ranked by change — and implicitly separates itself from jodi_oil_series, which it points to only for enumerating flow/product values. An agent can tell what this tool produces 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?

Maps real user questions to concrete invocations ("which Gulf producers raised crude output most this quarter" → months_back:3; "Saudi crude exports vs a year ago" → countries:["Saudi Arabia"], months_back:12), which is strong routing guidance. It never states when NOT to use it (e.g. use jodi_oil_series for raw unranked series), so the exclusion half is missing.

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