Get Mailbox Session

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

Annotations already declare readOnly, idempotent, non-destructive, open-world behavior, so the safety profile is covered. The description adds that the call returns capabilities, limits, and endpoint metadata, which is useful orientation, but it says nothing about caching/ETag behavior, credential scoping implications, or whether capabilities are static or account-dependent. Given the rich annotation set, this is adequate but not rich.

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 sentences, zero filler, with the primary use case front-loaded before the exclusion. Every clause earns its place and nothing is repeated from the schema or annotations.

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, full parameter documentation, and rich annotations, the description only needs to establish when to call this versus siblings — which it does. The only residual gap is that it does not hint at the ETag/caching workflow or multi-mailbox scoping tradeoffs, which are behavioral rather than structural concerns.

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% and both parameters carry their own explanatory text, including the conditional guidance for mailbox_id and the 304 semantics for If-None-Match. The description adds no parameter meaning beyond the schema, so the baseline of 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?

The description gives a concrete verb ('discover') and enumerates the resource contents (capabilities, limits, endpoint metadata), which is far more specific than the name 'get_session' alone. It also explicitly carves out message search, distinguishing it from the many mailbox_search/list siblings. It stops short of stating what a 'session' object is, but the purpose is unambiguous.

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?

Explicit timing guidance ('use this before complex mailbox work') plus an explicit exclusion ('do not use it for message search') is strong when/when-not coverage. It loses a point because the exclusion does not name the alternative tool the agent should call instead, forcing the agent to locate a search sibling on its own.

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