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

With no annotations provided, the description carries the full burden. It discloses spending credits, returns observation_id or workflow_id, and mentions the write-tier approval requirement. It also gives the connection precondition. While it doesn't detail error handling or idempotency, it covers the key behavioral aspects an agent needs.

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?

The description is well-structured: the first sentence states the core action and purpose, the second gives usage context, and the third (in brackets) covers approval. It is concise without being terse, though the approval note could be considered extra. Front-loaded with the primary function.

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?

For a simple tool with three required and fully-described parameters, the description provides enough context: what it does, what it returns, cost implications, and prerequisites. It doesn't explain error cases or edge behaviors, but those are not essential for a straightforward scan operation.

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 description coverage is 100%, so all three parameters are already documented. The description does not add extra meaning to the parameters themselves. Per the rubric, baseline for high coverage is 3, and the description provides no additional param-level detail.

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 description states a specific verb ('Run'), resource ('Replay Vision scanner'), and scope ('against one session recording now'). It clearly distinguishes from sibling tools like posthog_create_vision_scanner (creates scanners) and posthog_list_vision_observations (lists observations), leaving no ambiguity about what this tool does.

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 explicitly states the use case ('Use when you want one recording scored now') and a precondition ('Only works if PostHog is connected'). It doesn't explicitly name alternatives or when-not-to-use scenarios, but among the sibling tools there is no direct competing scan tool, so the guidance is sufficient for the intended context.

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