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

Annotations already flag destructiveHint=true, idempotentHint=true and openWorldHint=true, and the description adds the consequences those hints cannot express: held funds return to the Principal's withdrawable balance rather than the card, and the Listing Fee returns as Platform Credit. That is exactly the post-invocation impact an agent needs before committing to a destructive call.

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?

Purpose, endpoint, and the sibling fallback are front-loaded and waste nothing. The trailing instruction about how to phrase things for the Principal is presentation guidance rather than invocation guidance and runs long.

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 carries the burden of explaining the result, and it does so in financial terms (balance vs. card, Platform Credit). It stops short of describing the actual response shape or whether the Fee credit is immediate, but nothing essential to calling it correctly is missing.

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% and both params (id, idempotencyKey) are documented there. The description repeats the id format guidance ('without act_: aTdTkM-48271') already present in the schema and says nothing about idempotencyKey, so it adds little beyond the structured fields.

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 ('take ... off the board') and resource ('an errand (ACT)'), and pins it to the concrete endpoint POST /api/v1/acts/{id}/withdraw. The precondition 'no Human has claimed' immediately distinguishes it from cancel_act.

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 precondition ('no Human has claimed') plus an explicit alternative rule: 'Once a Human has claimed it, cancel it with cancel_act instead.' Both the when and the when-not are stated with the sibling named.

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