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

Even though annotations already mark it read-only and idempotent, the description adds substantial behavioral context: websites where the user is only a member are never available over MCP and not listed, credits cannot be bought through this server, and the return includes credit balances and subscription details. This goes well beyond the annotation hints.

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 description is a single long sentence but it is dense and information-rich, starting with 'Recommended first call' and systematically covering websites, roles, credits, and plan. It could be split for easier scanning, but no sentence or clause is wasted.

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 zero parameters, strong annotations, and an output schema present, the description is complete. It explains the return semantics, the website_id dependency for other tools, and the credit purchase limitation, giving the agent everything needed to decide when and how to call it.

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 has zero parameters, so there is no parameter-level semantics to explain. The description appropriately focuses on what the response contains, which is the relevant semantic content for a no-input tool.

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 states a specific verb and resource: it 'Returns the signed-in user's email and every website this connection may use' with detailed fields. It explicitly positions itself as the 'Recommended first call,' differentiating it from account-related siblings like get_credit_balance and get_website_settings.

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?

The description gives clear usage context: it is 'Recommended first call' and explains that website_id is 'needed by the other tools' when multiple websites exist. It does not name specific sibling alternatives or state when not to use it, but the first-call guidance effectively signals when to invoke it.

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