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

Annotations already declare readOnlyHint=false and destructiveHint=true, so the mutation risk is covered by structured data. The description adds genuine behavioral context beyond that: exposure defaults to secret, Cloud publish copies only public values into the static page, and there is no server runtime — all of which shape how an agent should set values. It stops short of saying whether delete is irreversible or whether set overwrites existing keys.

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?

Four tight sentences, front-loaded with the action and scope, followed by the three behavioral facts that actually change how the tool is used. Nothing is redundant and no sentence is filler.

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 six-parameter mutation tool with no output schema, the description covers the domain-specific pitfalls well (secret default, public-only Cloud copy, no runtime). It leaves gaps around per-action parameter requirements and what a list response or a delete returns, which an agent would still have to discover.

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 only 33%, so the description has to carry weight. It does map the four action values to the verbs and enumerates the product scopes, and it restates the secret/public default, but it never explains which name/value combinations are required per action, nor the projectId-except-Code rule beyond what the schema already says.

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 concrete verbs (list, set, update, delete) and a specific resource (owner-scoped env vars) plus the product scopes they apply to, so an agent knows exactly what domain it covers. No sibling in the supplied list overlaps this resource, so explicit differentiation isn't needed, but the four-in-one action surface is only loosely framed.

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?

Usage is implied rather than stated: an agent can infer this is the only env-var tool among the siblings. The caveat 'There is no server runtime' is useful orientation, but there is no explicit when-to-use/when-not guidance and no statement of prerequisites (e.g., that projectId is needed outside Code).

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