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

Annotations already declare destructiveHint=true and idempotentHint=true, so safety is covered structurally. The description adds real value beyond that: it says the current name is overwritten and that any field named in update_mask other than displayName is cleared or reset to its default — a non-obvious side effect an agent must know. It does not mention permission requirements, which keeps 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?

The operative content is front-loaded in two tight clauses with the destructive caveat attached directly to the field it concerns. The trailing 'Tools revision: d80f65c0.' is noise that earns no place in a tool description.

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 three-parameter mutation with an output schema and full annotation coverage, the description supplies the scope, the overwrite consequence, and the update_mask hazard — enough to call it correctly. Only resource-name formatting and auth expectations are left implicit.

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 0%, so the description carries the burden, and it does: name is identified as the resource name, display_name as the sole mutable field, and update_mask gets an explicit warning about what other values would do. It stops short of format examples (e.g. the resource-name pattern), so a 5 is not warranted.

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 ('Rename a custom dimension') and immediately narrows scope to display_name only, which separates it from ga4_create_custom_dimension and ga4_update_custom_metric without needing the sibling schemas.

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 operative guidance: rename only, and keep update_mask as displayName. It does not name an alternative tool or an explicit when-not-to-use condition, but the implied usage context (renaming an existing dimension) is unambiguous.

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