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

There are no annotations, so the description carries the behavioral disclosure burden. 'List' signals a read-only operation, and the description adds meaningful behavior beyond the tool name by saying it reports free status availability and identifies which counterparties support paid Preflight. It does not mention staleness or network dependency, but for a zero-parameter listing tool this is reasonably complete.

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?

One tight sentence with the verb and core subject front-loaded. Each clause adds a meaningful piece of information — registered counterparties, free status availability, and paid Preflight support — with no filler or redundant phrasing.

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 zero-parameter list operation with an output schema available, the description provides enough for an agent to invoke the tool correctly: it states what is listed and what attributes are reported. The only minor gap is lack of guidance on how this relates to sibling tools, but that is not required to make the call 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?

The input schema has zero properties and coverage is effectively complete, so there are no parameters whose meaning the description must clarify. The zero-parameter baseline is 4, and no further parameter-level explanation is needed.

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'), names the exact resource ('registered AgentObserver counterparties'), and specifies the useful qualifiers ('free status availability' and 'paid Preflight' support). It clearly distinguishes this tool from sibling tools by stating exactly what kind of information targets provides.

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 when to use the tool: when a caller needs registered counterparties and their Preflight/status availability. However, it does not explicitly contrast the tool with siblings such as agentobserver_preflight or agentobserver_status, and it gives no exclusions or alternative routing guidance.

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