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

Annotations already declare destructiveHint=true, idempotentHint=true, and readOnlyHint=false, and the description is consistent with a mutation. It adds the at-least-one-field precondition but does not explain what makes the call destructive (e.g., that passing source replaces existing code wholesale) or what permissions are needed. With annotations carrying the safety profile, this is adequate but thin.

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?

Two short sentences, zero filler, with the mutation scope front-loaded and the invocation constraint immediately after. Nothing could be cut without losing 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?

An output schema exists, so return values need no explanation, and annotations cover the safety profile, leaving the description to explain scope and preconditions — which it does. The only gap is behavioral consequence (what happens to prior source on replacement, effect on in-flight runs), which is not addressed.

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, and the description earns an extra point by stating a cross-parameter constraint not encoded in the schema: at least one of source/schedule/enabled must be supplied even though only project_id and cron_id are marked required. It adds no syntax detail beyond the schema, which already documents the 5-field UTC expression and TypeScript source.

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 plus the three mutable fields (source, schedule, enabled flag), which is far more informative than the title alone. It doesn't explicitly distinguish itself from siblings like projects_cloud_cron_create or projects_cloud_cron_run, but the field list makes the mutation scope unambiguous.

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?

"Pass at least one of those fields" gives a usable invocation precondition, which is real guidance. However, there is no when-to-use framing against alternatives such as cron_run (execute now), cron_create (new cron), or cron_get (read), so the agent must infer routing from tool names.

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