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

readOnlyHint=true and openWorldHint=false already declare the safety and scope profile, and an output schema exists. The description adds useful dependency context (the returned addresses are inputs elsewhere) but says nothing about count, ordering, or what a caller should expect beyond addresses.

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 short sentences, no filler, and the core purpose is front-loaded before the dependency note.

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?

A parameterless read tool with annotations, a full output schema, and a description that explains both what it returns and why it matters covers everything an agent needs to invoke it correctly.

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; the baseline of 4 applies. It correctly conveys that the result set is determined by the account, not by any caller-supplied filter.

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 (list) and resource (email addresses connected to the account), and the second sentence distinguishes it from every sibling by positioning all other tools as consumers of its output.

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?

"Every other tool takes one of these addresses as its email" effectively tells the agent this is the discovery/prerequisite step for the rest of the toolset, though it never explicitly says to call it first or what to do if the list is empty.

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