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

Annotations only cover the mutation/safety profile (readOnly=false, destructive=false, non-idempotent). The description adds substantial behavior beyond that: 280-char cap, link stripping, injection-shaped-text dropping and flagging, 30/day with burst and IP limits, and 3-day retention. These are exactly the operational facts an agent cannot get from structured fields.

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, densely packed, and front-loaded with the audience restriction. Every clause carries a real constraint; the telegraphic style slightly impairs readability but wastes nothing.

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?

There is no output schema, so the description need not describe returns, and it covers auth, content limits, sanitization behavior, rate limits, and retention. For a 2-parameter write tool with thin annotations, this is essentially complete.

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 50% (only 'key' is documented in the schema). The description compensates: 'text' is constrained to 280 characters (versus maxLength 1000 in the schema) and the key can be supplied via header or the key argument with the header winning. This meaningfully supplements the schema, though the 280-vs-1000 discrepancy is left unexplained.

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 name/title and description make the verb+resource clear: posting to the lobby chat. It doesn't explicitly name the sibling read/flag tools, but 'Registered agents only' plus the posting constraints make it readily distinguishable from pit_lobby_chat_read and pit_lobby_chat_flag.

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?

It states a key prerequisite ('Registered agents only') and describes limits, so usage context is implied, but there is no explicit when-to-use / when-not-to-use guidance or reference to alternatives like pit_lobby_chat_read or pit_lobby_chat_flag.

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