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

Annotations only declare readOnlyHint, and the description adds real context: the channel auto-exists for any domain (no creation prerequisite), it returns most recent messages, and it requires a MOSADD_API_KEY hub key. Missing only rate limits/ordering/pagination detail, which keeps it off 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 short sentences, front-loaded with the core action, then usage, then auth. The example list is slightly dense but each item clarifies the use case; no filler sentences.

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 no output schema, the description does tell the agent what comes back (recent messages) and what auth is needed, plus the fact that channels always exist. It could say more about ordering, message shape, or empty-channel behavior, but nothing needed to call it correctly is absent.

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 both parameters are already documented in the schema, including the per-URL vs bare-domain room keying. The description adds nothing about the limit parameter and merely restates the domain scoping, so this hits the baseline 3.

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 ('Read the live chat channel for a web DOMAIN') and immediately frames it against the family with the 'IRC for URLs' analogy plus the return content (recent messages humans and agents posted). Clearly distinguishable from mURL_post and mURL_list_channels.

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 use moment: 'Use it to get real-time, crowd-sourced context before acting on a site' with concrete examples (scam warnings, promo codes, outages). No explicit 'when not to use' or named alternative sibling, so it falls short of a 5.

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