Plan a GTM trigger change

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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description reinforces this with 'nothing is written' rather than contradicting it. It adds genuinely useful context beyond the annotations: the plan-then-apply handoff via google_apply and the fingerprint dependency (from gtm_get_trigger) for updates. It does not describe the plan artifact returned or its lifetime, which keeps it from 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?

Two sentences, front-loaded with the critical 'PLAN (nothing is written)' signal, followed by the operation and the apply handoff. No filler; every clause carries 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?

For a plan-only tool with no output schema, the description covers the essentials: the no-write guarantee, the workspace constraint, the update fingerprint path, and the apply step. It omits how the resulting plan is retrieved or reused (e.g., via plan_get), which is a minor gap against the plan_* sibling ecosystem.

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 100%, so every parameter (trigger, client_id, trigger_id, fingerprint, workspace_id) is already documented in the schema, including the update-only fingerprint requirement. The description only echoes the fingerprint-for-update point, adding no syntax or format detail beyond the schema. Baseline 3 applies.

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 (plan/create-or-update) and resource (GTM trigger) with a scope qualifier ('non-default workspace of the client's GTM container'), and the PLAN/nothing-is-written framing immediately separates it from the sibling gtm_plan_tag_upsert and gtm_plan_variable_upsert. An agent can identify exactly what this tool 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 a clear workflow: use this to stage the change, then 'Apply with google_apply after the user agreed.' This tells the agent when to invoke it and what the follow-up is. It stops short of explicit when-not conditions or naming alternative plan tools, but the resource type plus the plan/apply pattern is unambiguous.

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