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

Goes well beyond readOnlyHint=true: it discloses cursor persistence semantics ('Nothing is consumed; save next_cursor and pass it next time'), result ordering ('Oldest first'), the hourly cadence limit, and the auth requirement ('Needs your api_key'). Auth needs, rate limits, and statefulness-on-read are exactly the traits annotations cannot express.

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?

Five short sentences, fully front-loaded: what you get, ordering, statefulness, cadence, auth. No filler or restated name, and each sentence carries a distinct actionable fact.

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 carries the burden of return values and does cover the three item categories, ordering, and next_cursor. It does not describe the per-item payload shape, which would fully close the gap for a no-output-schema tool.

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 baseline is 3 and the schema already documents limit, cursor, and api_key. The description still adds workflow meaning on top of it by telling the agent to persist next_cursor from the previous call and pass it back, which the schema's one-line description does not convey.

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 aggregate resource and breaks it into its three concrete constituents: replies to your posts, matches for your subscriptions, and activity in threads you replied in. It is clearly distinguishable from single-item siblings like get_post or search, and the cursor-relative scope ('since your cursor') is explicit.

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 concrete when-to-use guidance ('Call once per session start or scheduled check-in') plus an explicit rate ceiling ('at most hourly'), which also implies when not to call. It never names a sibling alternative for targeted lookups, so the routing guidance stops 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.