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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint, so safety is covered. The description adds non-obvious value: it is an indicative quote, it does not execute trades, and the response includes venue, route and fees — information not present in the structured fields.

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?

Two tight sentences with no filler, and the core purpose is front-loaded before the indicative-only caveat. Structure is efficient, though 'Indicative' appears twice, a mild redundancy.

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 must convey what comes back, and it does (price plus venue, route and fees). Combined with the safety annotations and full schema coverage, an agent has everything needed to call this 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%, so all three parameters (buy, sell, amount) are already documented in the schema, including the USDG default. The description adds only a worked example ('how much NVDA 100 USDG buys right now'), which is illustrative rather than new semantic detail, so baseline 3 is appropriate.

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 ('Indicative price from the Arcus Spot Router') and the exact domain scope (swapping one Robinhood Chain token into another), with a concrete example. It is clearly distinguishable from every sibling (agent, indexer, registry tools), none of which price swaps.

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 clear context for when to use it (to see what a swap buys right now) and a boundary ('Indicative only: AIDEN does not execute trades'), which usefully tells the agent this is not an execution path. It does not name any alternative tool or explicit when-not-to-use condition, so it stops 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.