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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds valuable behavior beyond annotations: the GRADE RULE (OBSERVED/REPORTED/MODELLED, with a clear prohibition on quoting modelled values), the fact that no API key is required, and a specific detail about check_agreement ('the failed one that suspended the Indian series'). These enrich the agent's understanding without contradicting 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?

The description is compact yet information-dense: it lists sub-tools, explains the grade rule, notes when not to use it, and mentions no API key requirement. It is front-loaded with the router's purpose and structured with a list and a rule, with every sentence serving a functional purpose.

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?

As a router with four sub-tools and no output schema, the description adequately covers the calling convention (call with {tool, arguments}), provides an example, explains the grade rule, and gives routing context. It does not detail return formats for each sub-tool, but that is not critical since the sub-tools are separate operations and the description gives enough to invoke them correctly. The note about primary tools helps agents decide when this router is unnecessary.

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% (both tool and arguments have descriptions). The description goes beyond the schema by giving a concrete example argument object for describe_series ('{series: "tt010.china.burden"}') and clarifies that arguments are sub-tool-specific. This adds practical meaning to the generic 'That sub-tool's own arguments' in 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?

The description clearly identifies the tool as a router to the ledger's registry tools and enumerates all four sub-tools with concise one-line explanations. It explicitly distinguishes itself from sibling trade/tariff tools by stating 'Most questions never need this router', so an agent can immediately tell when this is relevant.

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?

Provides explicit guidance on when not to use it ('Most questions never need this router: trade/tariff answers live in the primary tools') and implies when to use it via the sub-tool list. It names the sub-tools and their purposes but does not explicitly exclude individual sibling tools beyond the general routing rule, which is acceptable for a meta-tool.

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