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

No annotations are provided, so the description carries the full burden. It clearly states the tool 'list all' relevant message types and includes 'required fields and stablecoin-specific extensions', which is transparent about the primary behavior. However, it does not disclose response format or any limitations, but for a read-only list tool the main behavior is adequately disclosed.

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, tightly-worded sentence that front-loads the action verb 'List' and immediately specifies the scope and content. Every word adds value with no redundancy or filler.

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?

Given the tool's simplicity (one optional parameter, no output schema), the description provides enough context to understand its purpose and content. It defines the scope (stablecoin/crypto payments) and the included details (required fields, extensions). The only missing context is the domain filter, but that is covered by the input schema.

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 has one optional parameter 'domain' with a complete description, providing 100% schema coverage. The tool description adds no additional meaning about the domain filter, so the baseline score of 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?

The description uses a specific verb 'List' with a clear resource 'ISO 20022 message types relevant to stablecoin/crypto payments' and specifies the content ('required fields and stablecoin-specific extensions'). This distinguishes it from sibling tools like generate_pacs008 or validate_message, which have different purposes.

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 implies usage for stablecoin/crypto payment scenarios, but does not explicitly say when to use this tool over alternatives, nor does it mention any exclusions. It provides a general context but no clear guidance on selecting this tool versus others.

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