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

Beyond the annotations, the description discloses material behavior: "Defaults to enabled=false so it does not start spending PostHog Vision credits until you set enabled=true." It also reveals the write-tier approval flow, including that "a just-once approval re-asks next time" and that the agent should "call it on the first clear ask." This adds meaningful operational context beyond readOnlyHint/destructiveHint.

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 compact and front-loaded: purpose, default behavior, usage trigger, prerequisite, then approval guidance. Every sentence contributes useful decision or invocation information; there is no filler or redundant restating of the tool name.

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?

Given the rich schema, annotations, and 10 parameters, the description covers the key operational needs: prerequisite connectivity, cost/credit behavior, default disabled state, and approval handling. It does not mention the return value or success response, but no output schema exists and the description still feels sufficient for an agent to select and invoke the tool correctly.

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?

The schema already describes all 10 parameters with detailed explanations, including the enabled default and the prompt's alternative placement on scanner_config.prompt. The description mostly restates this information rather than adding new parameter-level meaning, so the baseline of 3 for high schema coverage applies.

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 and resource: "Create a Replay Vision scanner on the connected PostHog project for the operator or analytics agent." It further clarifies the purpose as "adding a new AI probe on session recordings," which distinguishes it from sibling tools like posthog_update_vision_scanner and posthog_delete_vision_scanner.

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?

The description explicitly says when to use it: "Use when adding a new AI probe on session recordings," and provides a prerequisite: "Only works if PostHog is connected." It also includes write-tier approval guidance about first use and when to call. It does not name an alternative tool or state when not to use it, so it 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.