vexo_count_events

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

The description extensively covers behavioral traits beyond annotations: automatic range splitting with dedup, definition of 'dimension' (including metadata keys), handling of optional parameters, output format (window, group_by, rows, truncated, total_count), sorting, and error responses. Annotations already declare readOnlyHint and openWorldHint, and the description adds significant context.

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?

Well-structured with a summary sentence, bullet inputs, and output format. Slightly verbose but each section adds value. Could be tightened slightly but overall efficient.

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 no output schema and complex nested parameters, the description fully covers inputs, output shape (with optional fields), sorting, and error case. It leaves no major gaps for an agent to understand the tool's behavior.

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 only 50%, but the description provides detailed semantics for all parameters: ISO date format with inclusive end, optional group_by falling back to server config, filter_values max 200, filters with examples, and event_names. It also explains the dimension concept comprehensively.

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 clearly states the tool aggregates event counts over a date range with optional grouping, explicitly calling it 'the workhorse for cohort comparison,' which distinguishes it from sibling tools like vexo_event_timeline or vexo_get_recent_events.

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?

Strong usage context is provided: designed for cohort comparison, automatic splitting of ranges >31 days. However, it does not explicitly state when not to use this tool or compare to alternatives, so it falls 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.