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

With no annotations, the description must carry the full burden of behavioral disclosure. It states the action and preconditions but does not mention permissions, side effects, reversibility, or what the response/error behavior looks like. For a mutation operation like cancellation, this is a significant gap.

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 a single, front-loaded sentence with no filler. Every word contributes to the core purpose, making it easy to parse and remember.

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 mutation tool with no annotations and no output schema, the description is incomplete behaviorally: it does not explain what happens on success/failure, whether cancellation is reversible, or any additional requirements. The simple 2-parameter schema covers inputs, but the operational context is insufficient for an agent to confidently call the tool.

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?

The input schema already provides descriptions for both parameters, achieving 100% schema coverage, so the baseline is 3. The description does not add parameter-level meaning beyond the schema; 'owned .i domain' loosely maps to domainName and sellerAddress but adds no syntax or format details.

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 uses a specific verb ('Cancel') with a specific resource ('marketplace listing') and adds qualifiers ('active', 'owned .i domain') that clearly distinguish it from related operations. This differentiates it from siblings like marketplace_list_domain, marketplace_cancel_offer, and marketplace_buy_domain without needing to inspect those tools.

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?

The description gives clear context that the tool applies only to active listings for owned .i domains, implying when to use it. However, it does not explicitly name alternatives or state when not to use it, leaving the agent to infer the boundary from sibling tool names.

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