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

Beyond the annotations (readOnlyHint=false, idempotentHint=true, destructiveHint=false), the description discloses the required scope, the plan tier, and a genuine side effect – re-running the claims check when copy or destination changes, which can make the edit fail. It does not describe what happens to fields omitted from the request or what the response contains, which matters for a PATCH-style mutation.

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 compact block: scope and access tier are bracketed up front, the edit surface is stated next, and the failure mode and pricing follow. The trailing '(Wraps PATCH /api/v2/hook-studio/ctas.)' is low value for an agent choosing a tool, though useful for debugging.

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 12-parameter mutation with no output schema, the description covers the essentials: what can be changed, the claims-check re-validation, scope and plan prerequisites. It leaves open whether omitted fields are preserved (partial vs. full replace) and whether the updated CTA is returned, which are the main remaining gaps.

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 50%, and the description names and groups the goal fields (goalKey, isPrimary, paidEligible, adButton) plus status and the 'copy'/'destination' concept, which is real framing value. However, it adds nothing for offerId, platforms, card, line or brandId beyond what the schema already says or fails to say, so it only partly compensates for the coverage gap.

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 uses a specific verb and resource ('Edits a CTA, its status or its goal fields') and enumerates the goal fields (goalKey, isPrimary, paidEligible, adButton), so the effect is unambiguous. It does not explicitly contrast with siblings like ctas_create, cta_settings_update or update_content, leaving the agent to infer the boundary from the name.

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?

It gives concrete preconditions that gate correct invocation: a `write` scope, the Pro plan or higher, and the fact that new copy or a new destination re-triggers a claims check that can block approval. It stops short of naming alternatives (e.g. cta_check to pre-validate, ctas_create for new records) or stating when not to use it.

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