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

Annotations already declare readOnlyHint=true, destructiveHint=false and idempotentHint=true; the description is consistent with them ('opens nothing by itself') rather than contradicting. Beyond the annotations it discloses the actual behavior that matters — the return is procedural guidance with screens, buttons and fields, not a mutation — which the annotations alone would not convey. It does not describe the shape or length of that returned guide.

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 core workflow is stated early, but the sentence is overloaded with semicolons and parentheticals, and the trailing API paragraph with 'checked 22 Oct 2026' is background trivia that does not help an agent decide or call. The 'from ChatGPT, Claude or any AI agent' clause adds no selection value.

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 must carry the return-value burden, and it does: it says the result is a step-by-step walkthrough of screens, buttons and fields. It also supplies the missing piece of the workflow — which tool family performs the actual action. What's absent is any hint of how long the returned guide is or what to do if a step fails.

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?

The tool takes zero parameters, so there is no parameter meaning to add; the baseline for a parameterless schema applies. Nothing in the description misrepresents the empty input contract.

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 names a specific resource (a subscriber in the user's own Campaign Monitor account) and explicitly corrects the misleading tool name by stating it 'Returns how to do it in Campaign Monitor step by step ... and opens nothing by itself.' That disambiguation is clear, but the opening imperative 'Add subscriber' still reads as if the tool performs the write, and no distinction is drawn from the other campaign_monitor_* guide siblings.

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 an explicit execution path: this tool first, then 'do it with the cotlet_browser_* tools in the user's Campaign Monitor Cloud Browser.' It also pre-empts the obvious alternative by noting Campaign Monitor has a REST API but 'no official MCP server,' so the agent won't look for a direct API route. No explicit when-not-to-use condition is given.

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