list_instances

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

With no annotations, the description carries the burden of behavioral disclosure. It reveals that listing is scoped to a zone and the default zone behavior, and 'List' implies a read operation. However, it does not mention pagination, authentication, or other operational caveats.

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 brief and front-loaded: the first sentence captures the core purpose, followed by a clear args block. Every word contributes value without redundancy.

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?

The tool has one optional parameter and an output schema, so return values do not need explanation. The description adequately covers the only parameter and scope, though a brief note about pagination or read-only semantics would make it fully complete.

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 schema only defines zone as an optional string with a null default. The description adds real meaning by providing example zone values and stating that the default zone is used when omitted, which is essential for correct invocation.

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 'List all compute instances in a Scaleway zone' with a specific verb, resource, and scope. It distinguishes itself from siblings like get_instance (single instance) and create_instance/delete_instance (mutations).

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 it: to list all compute instances in a zone. It mentions the zone parameter and its default behavior, but does not explicitly contrast with alternatives like get_instance or state exclusions.

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