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

Annotations already declare readOnlyHint=true, so the 'Read-only' restatement is redundant, but the description goes well beyond them: it explains that unverifiable access postures are 'counted as unverified, never as clean' and that access_posture is 'null under an add-on scope'. Those are non-obvious counting/nulling semantics that an agent would otherwise have to guess, though it says nothing about permissions needed or result size.

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 tool's identity and scope before the long field enumeration, and with no output schema the enumeration of returned content earns its space. However it is a single dense run-on sentence, and the access_posture clause in particular is heavy enough to slow parsing.

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 usefully enumerates what comes back and flags the unverified/null semantics, and it states the sibling boundary. What it lacks is any mention of auth requirements, freshness windows beyond 'scanner freshness', or the shape of the access_posture counts.

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 parameters are self-documenting ('Scope the overview to one add-on', 'omit for the whole fleet'). The description adds only marginally — the note that access_posture is null under an add-on scope is the one real semantic addition about parameter effect. Baseline 3 is appropriate when the schema carries the parameter burden.

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?

Names a specific resource and scope ('the organisation's fleet-wide Security Center summary') and enumerates the concrete content (severity totals, fixable count, CISA KEV exposure, scanner freshness, access_posture counts). It also explicitly distinguishes itself from get_security_reports as 'the fleet rollup' versus the 'per-cluster Trivy summary', so an agent can separate the two 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?

Gives clear usage context: 'Optionally scoped to one cluster or one add-on' and 'This is the fleet rollup; get_security_reports is the per-cluster Trivy summary.' That routes the agent away from one sibling, but no guidance is given relative to the other security overviews (get_security_compliance_overview, list_security_cluster_posture) and no explicit when-not-to-use statement.

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