list_instances

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

With no annotations, the description carries the full burden. It discloses the key behavior: it lists all instances owned by the wallet and returns specific fields. It stops short of explicitly stating it is read-only or describing pagination, but for a simple list operation, the provided transparency is adequate and adds context beyond a bare statement.

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 two sentences long and entirely purposeful. The first sentence states the core function, and the second clarifies the return contents. No filler or irrelevant details are present.

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 tool with no parameters, no annotations, and no output schema, the description is complete. It explains both what the tool does and what information it returns, which is sufficient for an agent to invoke and interpret the result without needing further clarification.

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 no parameters, so the 0-parameter baseline applies. The description adds no parameter documentation, but none is needed. It correctly implies that no parameters are required for the tool.

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 clearly states the action ('List all VPS and Node instances') and scope ('owned by the wallet'), using a specific verb and resource. It also enumerates the return fields (IDs, types, statuses, subscription dates), which distinguishes it from siblings like get_instance (single instance) and list_products (different resource).

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 this tool by stating it lists all wallet-owned instances, but it does not explicitly contrast with alternatives like get_instance (for a specific instance) or mention exclusions. The word 'all' hints at its broader scope, but no direct when/when-not guidance is provided.

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