zia_list_vpn_credentials

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

Annotations already declare readOnlyHint=true. The description adds a meaningful security-relevant disclosure ('PSK never returned') that prevents an agent from misinterpreting a missing pre-shared key as an error or incomplete data. It doesn't address pagination, but for a simple list with strong annotations, this is a valuable, non-redundant contribution.

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?

Eight words, one parenthetical, zero waste — the description nails the 'less is more' test. It front-loads the verb+resource, then tacks on the single most important behavioral caveat without padding.

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 parameterless-but-for-optional-filters list tool with no output schema, the description plus the superb `query` schema docs cover the agent's needs. The PSK caveat preempts a common point of confusion. Slight deduction for not hinting at the shape or count of the response, though the operation's simplicity keeps the gap small.

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 description itself contributes no parameter info, but schema coverage is 50% — the `query` param has rich, example-laden JMESPath documentation (including the snake_case warning and the 'call once without filter' tip). The `search` param is undocumented in both places, capping this at baseline-3.

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+resource pattern ('List ZIA VPN credentials') and adds a crucial scope detail ('PSK never returned') that helps distinguish it from the dozens of zia_list_* siblings. It's immediately clear this is a read-only enumeration of VPN credential records, not the many URL/rule/location lists in the family.

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 provides no explicit when-to-use versus alternatives, but for a list operation the resource name + read-only annotation make usage self-evident. It doesn't fail, yet offers no explicit alternative or exclusion guidance either—middling but acceptable for the genre.

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