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

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), but the description adds genuinely non-inferable behavior: missing months return {reported:false, value:null} rather than 0, and the API is keyless. That null-vs-zero rule is the kind of detail an agent could not derive from schema or annotations.

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 scope, then flows, then example queries, then the null-handling caveat. Every clause carries information (flow coverage, null rule, keyless, example call) with no filler.

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 return-value burden and does disclose the reported/value null shape and the trailing-months window. It leaves end_month windowing behavior and any result envelope details to the schema, which is a minor gap for a data-series tool.

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%, so the baseline is 3, but the description adds meaning by clarifying that exports/imports can be returned as totals or split LNG vs pipeline, and by demonstrating flow+months+country together in an example. It doesn't explain end_month semantics beyond what the schema already says.

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 ('Monthly JODI-Gas series for one country') and enumerates the measurable flows covered, scoping it clearly against siblings like jodi_oil_series and jodi_gas_compare (which handles multiple countries). The example queries make the intended subject matter unambiguous.

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?

Three concrete example questions ('Qatar LNG exports over the last 3 years') show exactly what this tool is for, and 'for one country' implicitly separates it from jodi_gas_compare. It stops short of naming the alternative explicitly or stating when-not-to-use, so it falls just short of a 5.

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