vdi_list

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

Annotations only declare readOnlyHint=true; the description goes further by defining which VDIs count as orphaned (no VBD) and by spelling out the truncation contract ('when truncated is true there are more disks than were returned'), which is the key pagination behavior. It stops short of noting cost, rate limits, or required permissions, so not a 5.

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?

Front-loaded with the [READ] marker, purpose, and the filter semantics, then the return shape, then args. Mostly waste-free, though the Args block restates defaults already present in the schema (limit=200, null defaults), which is mild 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?

With no output schema, the description compensates by naming the returned keys (vdis, returned, limit, truncated) and all four parameters. A caller has enough to invoke and interpret a truncated result, with only minor parsing details left implicit.

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?

Schema description coverage is 0%, so the description carries the full burden and largely meets it: it labels sr as an 'SR uuid', describes orphaned_only's meaning, gives the limit default, and explains where target's value comes from (config, omit for default). Minor gap: it doesn't clarify interaction between limit and truncation.

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?

States a specific verb and resource ('List VDIs (virtual disks)') with two explicit scoping modes (per SR, orphaned-only). The resource is distinct from every sibling, so an agent can separate it from sr_list or vm_list without opening a schema.

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 explains what 'orphaned' means and calls the results 'candidates for reclaiming space', which implies when the filter is useful. However, it never states when to use vdi_list versus sr_list or vm_list, nor any exclusions or prerequisites, so routing is left to inference.

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