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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds substantive context beyond them: the Sales Navigator subscription prerequisite (has_sales_nav), what is returned (threads with messages and participant profiles), and the pagination contract. It omits rate limits or quota behavior, keeping it short of a 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?

Four dense sentences with no filler: purpose, prerequisite, return shape, pagination, then routing. The prerequisite and the sibling routing are front-loaded where an agent will read them.

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 a full parameter schema, an output schema, and rich annotations, the remaining burden is routing and prerequisites, both of which are stated. Nothing an agent needs in order to call this correctly is missing.

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 description coverage is 100%, so all four parameters are already documented. The description restates the pagination flow (next_page_starts_at as page_starts_at), which duplicates the schema's own wording rather than adding syntax or edge-case detail. Baseline 3 applies.

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 (list Sales Navigator messaging threads) and grounds it in the API surface (salesApiMessagingThreads). It explicitly distinguishes itself from the classic-inbox sibling list_conversations, so an agent can route correctly without opening either schema.

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 an explicit precondition ('Only when the account has Sales Navigator and the user asks about that inbox') and names the alternative with the condition that selects it ('the classic inbox is list_conversations'). When-to-use and when-not-to-use are both covered.

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