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

Annotations already declare readOnly/idempotent/openWorld, so safety is covered; the description adds genuinely new behavior that annotations cannot express: a ~20-second worst-case latency and that returned paths may be non-optimal. It stops short of describing truncation, error modes, or how 'source cost' is reported, so not a 5.

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-loaded one-line purpose followed by clearly labelled 'When to use', 'Prefer another tool', and 'Example' sections. Long but every sentence carries distinct routing or behavior 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?

Output schema exists, so return structure needn't be explained. Purpose, routing, latency caveat, and a concrete invocation example cover everything an agent needs to call this 7-parameter tool 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 description coverage is 100% and already documents every field, including the send_max/source_assets mutual exclusion and asset formats. The description adds no syntax beyond the example call, so the baseline 3 applies.

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 resource ('Multi-hop payment paths') plus the core output ('their source cost'), which is exactly what distinguishes it from the single-hop siblings. An agent can tell what it 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?

Explicit 'When to use' (before a cross-currency or multi-hop payment, to test route existence and cost) and explicit routing away to named alternatives: payment-readiness for direct payments, slippage for single-pair trade cost. Nothing left to inference.

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