Create service account key

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

With no annotations, the description carries the full burden and does well: it discloses that the private key material is returned base64-encoded in privateKeyData, that it cannot be retrieved again after this call, and that the output is a secret. It omits permission requirements (e.g., iam.serviceAccountKeys.create) and any key-type/rotation caveats, keeping it short of a 5.

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?

A single dense sentence front-loads the creation action, then the return format, then the irreversibility warning. Every clause earns its place, though the em-dash structure is slightly packed.

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 explains what comes back (privateKeyData, base64) and the critical one-time-retrieval caveat, which is exactly what an agent needs to avoid losing the key. It is only mildly incomplete on required permissions and the undocumented email parameter.

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 50%: projectId is documented in the schema but email is not, and the description says nothing about either parameter's syntax or default behavior. The phrase 'for a service account' loosely implies email identifies the target, but no meaningful semantics are added.

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 precise verb and resource (creates a JSON key for a service account) and distinguishes itself cleanly from the sibling list/delete service-account-key tools. An agent knows exactly what this does without opening the 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 operational guidance for the moment of use: save the key immediately and treat the output as a secret, because retrieval is one-shot. It does not, however, explicitly route to an alternative (e.g., prefer workload identity or list_service_account_keys) — it presumes the caller already wants a new key.

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