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

readOnlyHint=true already tells the agent this is a safe read. The description adds a genuinely non-obvious behavioral trait: the call fails without an authenticated Proof session, and start_login is the recovery path. It stops there, saying nothing about how many addresses typically come back or whether unverified/pending addresses are included, which matters for an email-listing tool.

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 purpose sentence is front-loaded and clean. The ACCESS paragraph, however, consumes more space than the tool's actual behavior and reads as cross-cutting boilerplate; roughly half the description is spent on authentication mechanics rather than on what the listing returns.

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 an output schema present, return-value documentation is unnecessary, and a zero-parameter read-only list tool needs little more than purpose plus the auth gate, both of which are supplied. What is missing is only minor: whether pending/unverified addresses are included and whether results are ever paginated.

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 semantics to explain and the baseline is 4. The schema is empty and correctly so; nothing in the description is needed here.

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?

Specific verb (list) plus resource (email addresses) with an explicit scope of the authenticated account. It is distinguishable from list_phones and the email-mutating siblings (add/set/remove), though it never names a sibling explicitly.

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 ACCESS block gives a real prerequisite (a Proof account, authenticate via /mcp or start_login) which is actionable usage context. However, it says nothing about when to prefer this over related tools like list_phones, get_current_user, or start_add_email for adding a new address; the guidance is auth-only, not selection-oriented.

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