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

Annotations only cover the read/write/destructive profile; the description adds substantial behaviour beyond them: precedence over organisation variables, the deferred re-render of interpolating stack members on the next reconcile, and a hard validation rule that secret-looking values are refused. These are exactly the side effects and constraints an agent needs before calling.

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?

Three dense sentences with the verb and scope front-loaded and no filler; the reconcile parenthetical doubles as a useful cross-reference. Slightly overloaded relative to a two-sentence ideal, but every clause carries information.

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 still covers the things an agent would otherwise need to guess: precedence over org variables, when the change takes effect, how to force it, and the secret-value restriction. Nothing material is missing for a 4-parameter upsert tool.

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 the baseline is 3, but the description adds a genuine constraint on the 'value' parameter (values that look like secrets are rejected) that the schema does not express. It adds no syntax for 'name' or 'cluster_id' beyond the schema, so it does not reach a 5.

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 ('Create or update (upsert) a variable on the current cluster') with clear scope, and distinguishes itself from the organisation-scope sibling by describing the override behaviour. An agent can separate it from set_organisation_variable, list_cluster_variables and delete_cluster_variable without opening any 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 context for when this tool is the right one (cluster-scoped variable that takes precedence over an organisation variable of the same name) and names an alternative path for secrets ('store secrets with SOPS instead'). It does not explicitly state when to prefer set_organisation_variable over this tool, so it stops short of full when/when-not guidance.

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