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

The annotations already declare readOnlyHint=true, so the redundant 'Read-only' adds little. However, the description adds genuinely useful behavioral context: null provider means the credential is gone, and the external-dns policy differs per provider (upsert-only for Cloudflare, sync otherwise), plus that the list merges cluster-local and inherited org-wide zones.

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?

It is information-dense and largely front-loaded, with the edge case (null provider) and safety note at the end. The first sentence is a long run-on with nested parentheticals, and the CLI-twin reference adds mild noise, but no sentence is purely filler.

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?

There is no output schema, so the description appropriately explains the shape of returned entries and the null-provider edge case. With only two optional cluster-scoping parameters fully documented in the schema, an agent has enough to invoke it correctly; only explicit sibling routing is missing.

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 100%, and both cluster_id and cluster_name carry their own descriptions including the 'optional when a cluster is selected' behavior. The description adds no further parameter detail, so the baseline 3 applies.

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+resource: it lists the DNS zones a cluster serves, covering both its own declarations and inherited organisation-wide ones, and enumerates the fields returned (credential, provider, external-dns policy). The cluster scope is implied by 'one cluster', which implicitly distinguishes it from list_organisation_custom_dns_zones, but that sibling is never named, so the differentiation is inferential rather than explicit.

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 describes what the tool returns but never says when to use it versus the nearby alternatives (list_organisation_custom_dns_zones, get_cluster_dns_zone, add/remove_cluster_custom_dns_zone). There are no exclusions or selection conditions, so an agent must infer usage entirely from the name.

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