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

With no annotations supplied, the description carries the full burden and does well: it discloses the payment requirement ($0.05 USDC per call via x402, paid through _meta["x402/payment"]), the free preview escape hatch, the hop ceiling, the graph scale (709,830 relations), and what each hop returns (relation plus source). It omits failure behavior when no path exists within 4 hops and any rate limits, which keeps it from a top score.

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?

Three sentences, front-loaded: capability first, then routing syntax, then cost and the free alternative. The leading 'World Combine.' restates the tool name but is the only wasted token; every other clause (hop cap, corpus size, per-hop metadata, payment header, sample flag) is operationally necessary.

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 paid, nested-parameter tool with no annotations and no output schema, the description covers what an agent needs before calling: what it computes, the cost and how payment is transmitted, the free preview option, and the shape of returned hops. Remaining gaps (no-path behavior, error format) are minor relative to what is disclosed.

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 real meaning the schema does not: the 'a*, b*' shape of the two entities inside the /combine route parameters. That resolves what would otherwise be an opaque query-string payload for a nested-object parameter.

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 concrete verb and resource: 'Find how any two world things are connected' via a 'shortest typed path (<= 4 hops)'. The mechanism and limit are specific enough to distinguish this from the many data-lookup siblings, though 'world things' is never defined as a node identifier format, which leaves a small ambiguity about input shape.

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?

Gives a clear context for use (connectivity between two entities) and offers a concrete low-risk alternative path via 'sample=true for a free 3-row preview'. It stops short of saying when not to use it, e.g. whether it is appropriate for bulk or symmetric lookups, or what to do when no path exists.

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