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

Annotations already establish readOnly, idempotent, non-destructive, open-world behavior, so the description's added value is the content disclosure: product inventory, account plan, contact usage, and the chat-vs-app capability split. That is genuine context beyond annotations, though it does not describe any response shape or freshness guarantees.

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, both load-bearing: the first front-loads the trigger and the routing instruction, the second enumerates the additional returned content. No filler or restatement of the tool name.

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 zero-parameter, read-only entry-point tool with no output schema, the description covers when to call it, what it returns at a summary level, and why not to substitute other tools. Only the practical granularity of the returned overview is left unspecified, which is a minor gap.

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?

Zero parameters, so there is nothing for the description to disambiguate; baseline for a parameterless tool applies. The description correctly spends its words on scope and return content instead.

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: it returns an overview of every product (Marketing Platform, API Platform, Email Verifier, add-ons) plus the account plan and contact usage. It also explicitly distinguishes itself from the sibling tool list by saying to answer from the overview 'not from the tool list.'

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 explicit trigger conditions ('when the user asks what you can do, what Mailercloud offers, or how to get started') and an explicit ordering instruction ('call this tool first'). The alternative (inferring capabilities from the tool list) is named and rejected.

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