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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so safety is covered; the description still adds genuine value by disclosing ordering (threads by recency, messages oldest first), content sanitization of HTML, and an explicit prompt-injection warning about untrusted message content. It stops short of describing paging behavior, so it is not a full 5.

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?

Three short sentences, front-loaded with the primary action and the mode split, then the trust warning last. No filler and nothing repeated from the schema verbatim.

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?

An output schema exists, so return values need no prose explanation, and the description covers both operational modes, ordering, sanitization, and the untrusted-content caveat. The only omission is pagination semantics for `cursor`, which is only inferable from the schema field itself.

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?

Schema coverage is 67%, and the description materially expands `threadId` by explaining both the omitted and supplied branches and the return shape of each. The two remaining parameters, `inboxId` and `cursor`, get no added meaning in the description, leaving a gap that the schema only partly fills.

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 concrete verb and resource ("Read an inbox") and then splits the behavior into two named modes keyed on `threadId`, so an agent knows exactly what each call returns. It does not, however, contrast itself with siblings such as volanea_search_inbox or volanea_wait_for_email, so the boundary with those tools is left implicit.

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 conditional guidance: omit `threadId` to list recent threads, supply it to open one conversation. What is missing is guidance on when to switch to a search-based sibling instead of browsing, and any note about using the cursor for continued paging.

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