Update tag (🟡 write)

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

Beyond the annotations, the description discloses three non-obvious behaviors: parameters merge by key with null meaning removal, the update is a read-modify-write protected by fingerprint against concurrent edits, and dry_run defaults to true so nothing changes unless explicitly disabled. These are exactly the details an agent needs before invoking a mutation with destructiveHint=false.

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 tight sentences, front-loaded with the action and capability list, then the two highest-risk details (merge semantics and concurrency safety), then the default preview mode. No filler and no repetition of schema fields.

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?

The tool is a 10-parameter mutation with an output schema, so return values need no explanation, and the description covers the risky parts: merge semantics, concurrency, and the dry_run default. The gap is minor — the role of `workspace_id` and `notes` and the required-vs-optional split are left entirely to the schema.

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 whole burden. It adds genuinely valuable semantics for `parameters` (merge-by-key, null removes) and maps prose to `name`, `paused`, `firing_trigger_ids`/`blocking_trigger_ids`, and `dry_run`, but leaves `notes`, `workspace_id`, `container`, and `tag_id` entirely unexplained.

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 opens with a specific verb+resource ('Change selected fields of an existing tag') and enumerates the concrete edits possible (pause/unpause, rename, swap triggers, set parameters). 'Existing tag' implicitly separates it from gtm_create_tag and gtm_get_tag, but no sibling is named, so the differentiation is inferred rather than stated.

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?

There is real workflow guidance embedded in 'dry_run=true (default) shows a before/after diff only', which tells the agent the safe default and the preview path. However, there is no explicit when-to-use / when-not guidance and no routing to alternatives such as gtm_create_tag or gtm_get_tag for read-only inspection.

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