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

Annotations already cover read-only, idempotent, non-destructive, so the bar is lower; the description still adds real value by disclosing that recent messages are returned only for private chats where the agent may write, and that the counterparty's text is isolated in an 'untrusted' field. It omits what happens when access is denied or the chat is missing.

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?

Three short clauses, front-loaded with the identity of the resource, then the returned fields, then the trust caveat. No padding; telegraphic style is dense but every clause carries information.

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 compensates by naming the returned components (counters, deadline, quote, recent messages, untrusted text). Adequate for a 2-parameter read tool; only the failure/empty-case behavior is unaddressed.

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% and the schema already explains 'after' as a cursor returning up to 8 newer messages via data.next_after. The description restates the cursor idea and adds the write-permission condition, but contributes little beyond the schema.

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+resource ('One chat by chat_id') and enumerates what comes back (counters, deadline, quote), which distinguishes it from list_chats. It never names the sibling explicitly, so the differentiation is implied rather than declared.

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?

Usage is only implied: the id parameter description points at list_chats/quest_status as the source of chat_id, and 'when the agent may write there' conditions the private-chat branch. There is no explicit 'use this instead of X when Y' guidance against list_chats or message-reading siblings.

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