User Event Breakdown

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

Annotations declare readOnlyHint=true, openWorldHint=true, idempotentHint=true, and destructiveHint=false, so safety and non-mutation are already established. The description adds useful behavioral context: it returns a per-event_name breakdown, checks both user ID types, and mentions accepted date forms (startDate/endDate and pastMinutesStart/pastMinutesEnd via schema). It could go further by noting whether an empty breakdown is returned for unknown users, but given the annotation coverage, a 4 is appropriate.

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 sentences, each earning its place: what the tool returns, the key input flexibility (userId), and a usage example. The most important information is front-loaded in the first sentence. No filler or repetition of schema details.

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?

The tool has 8 parameters but only 2 are required, and the optional parameters (filters, timeZone, pastMinutesStart/End) are already fully documented in the schema with 100% coverage. The description focuses on the decision-relevant part: how the userId is resolved and what the breakdown looks like. Since there is no output schema, a brief note on the response shape (e.g., a map of event_name to count) would make it fully complete, but the current level is adequate for correct invocation.

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 the baseline is 3. The description adds value by clarifying the semantics of the critical userId parameter (accepts either the Rybbit device hash or app-provided identified_user_id, both are checked) and by giving a concrete example of what the output means. The event_name filter dimension is also annotated in the schema but the description reinforces the per-event behavior. This exceeds the bare baseline.

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 ('Get'), a resource ('event count breakdown'), and a scope ('for a specific user'). It goes beyond a generic listing by explaining the output semantics ('how many times each event_name was triggered by this user') and even provides example event names. This distinguishes it from siblings like rybbit_get_site_event_count and rybbit_get_org_event_count, which are aggregate counts, and rybbit_get_user, which fetches user details.

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 clearly explains the key usage context: analyzing per-user behavior (e.g., ad_click, chat_message_sent) and the dual ID flexibility (device hash or app-provided ID). It implies when to use this tool versus site-level or org-level event count tools, though it does not explicitly name alternatives or state when not to use it. That slight gap keeps it from a 5.

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