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

Annotations already declare idempotentHint=true and destructiveHint=true; the description earns credit by explaining the idempotency mechanism ('the same value again changes nothing'), disclosing audit-logging, and giving the return shape. It does not spell out what happens to a pre-existing variable's environment scoping on replace, but the safety profile is otherwise well covered.

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 sentences, front-loaded with purpose and the sibling exclusion, then scope routing, then behavior and return contract. No filler; every clause carries information an agent needs.

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 6-parameter mutation tool with no output schema, the description covers purpose, scope selection, auth requirement, idempotency, audit side effect, and return value. Nothing material is left for the agent to guess.

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 coverage is 100%, so the baseline is 3, but the description adds real semantics the schema cannot: which optional parameters must be combined for which variable scope, and the token privilege requirement for org. That is added meaning beyond field-level descriptions.

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 ('Create or replace an Actions variable') and immediately scopes it away from the sibling case ('plain text, not for secrets — use gluecron_set_repo_secret'). An agent can distinguish it from set_repo_secret and delete_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?

Explicitly maps parameter combinations to outcomes: owner+repo for repository scope, owner+repo+environment for environment scope, org for organisation scope. It also names the alternative tool for secrets and the admin-token prerequisite for org variables, so when-to-use and when-not-to-use are both covered.

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