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

With no annotations, the description carries the full burden. It usefully discloses return contents and implies low cost, but "cheap" is unquantified, and it says nothing about authentication requirements, rate limits, or ordering of the returned items.

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, front-loaded with the nature of the call, then what comes back, then how to use the parameter. Every clause earns its place.

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?

No output schema exists, so the description must describe returns — and it does, listing summary, messages, invitations, and pending games. It omits cost specifics and error/incremental edge cases, but is sufficient for an agent to call 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?

Schema coverage is 100%, so the schema already documents both `since` and `token`. The description's "Pass since = latest_seq from your last inbox" largely restates the schema text, adding the incremental-polling intent but no new format or edge-case semantics.

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 resource (inbox) and enumerates its contents: a one-line summary, messages, invitations, games waiting on your move. This distinguishes it from siblings like list_games or send_private_message, though it never names an alternative 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?

"Cheap check-in" frames it as a low-cost polling operation, and "Pass since = latest_seq from your last inbox" gives the incremental-refresh pattern. It stops short of stating when not to use it or naming an alternative tool.

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