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

Annotations already declare readOnlyHint=true, and the description's 'Read-only.' is consistent with that. Beyond the annotation it adds real behavioral context: the exact data surface returned (findings split into observed vs actionable severity, known-exploited and fixable-severe counts, dispositions in force, scanner freshness), which tells the agent what state it is reading rather than just that it is safe.

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?

Effectively two sentences: the content enumeration is dense but front-loaded, and the sibling pointer comes last as it should. The long field list is justified because there is no output schema, though it reads as a run-on rather than cleanly structured.

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 carries the burden of explaining return values, and it does so thoroughly. Combined with the read-only disclosure, the sibling routing, and the schema-documented parameters, an agent has everything needed to select and invoke this tool correctly.

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%, so both addon_name and cluster_id (including the 'optional when conversation is bound to a cluster' behavior) are already documented in the schema. The description adds no syntax or format detail beyond that, 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?

The description names a specific verb+resource (security posture of one add-on on one cluster) and enumerates exactly what is returned: workloads with images, findings by severity, exploited/fixable counts, dispositions, scanner freshness. It explicitly distinguishes itself from the organisation-level sibling get_security_overview, so an agent can route without opening either 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?

It gives an explicit alternative and the condition that selects it: 'The organisation-level view of the same add-on is get_security_overview with addon_slug.' That is clear routing guidance, though it does not position the tool against the other cluster-scoped security siblings (e.g. get_cluster_stack_security, get_addon_security_updates) or state prerequisites.

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