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

Annotations already mark this as read-only and non-destructive, and the description adds beyond them: the grade rule (OBSERVED / REPORTED / MODELLED; modelled quantities are never quotable as measurements), the offer-counted-tonnes alternative, and contextual detail about the suspended India series. No API key requirement is also disclosed.

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 description is compact yet information-dense, front-loading the router purpose and sub-tool list. Every sentence earn its place: invocation, sub-tool descriptions, grade rule, usage disambiguation, and auth note.

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 router with no output schema and a nested arguments object, the description covers invocation, sub-tool selection, key domain constraints, alternatives, and auth. It is slightly less explicit about per-sub-tool argument schemas or return shapes, but the given context is strong enough for an agent to select and begin invoking it correctly.

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% for the router's two parameters with an enum for tool. The description adds meaning by showing the call shape '{tool, arguments}' and giving a concrete example argument object for describe_series. It slightly stops short of fully documenting the argument requirements of every sub-tool, but it conveys enough for a router.

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 clearly identifies the tool as a router to registry tools, enumerates all four sub-tools, and gives a one-line purpose for each. This distinguishes it from the trade/tariff siblings and leaves no ambiguity about the resource it operates on.

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?

It explicitly says 'Most questions never need this router: trade/tariff answers live in the primary tools,' giving when-not-to-use guidance and pointing to alternatives. It also states the invocation pattern and that no API key is required.

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