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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is covered. The description adds the important default that an unfiltered call scans every event on record, but says nothing about cost, expected result size, or what the response contains (no output schema exists). It is honest but not rich beyond the structured data.

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 compact sentences: the core action first, then the filter options in the order they appear in the schema, then the unfiltered default. No filler and no repetition of schema descriptions verbatim.

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 four-optional-parameter count with full schema coverage and annotations, the definition covers filters, ID provenance, time format, and default behavior. The only gap is the return value shape (presumably a single count), which is not stated and has no output schema to fall back on.

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 baseline is 3, but the description pays for more: it attributes version_id to list_versions and event_name_id to list_event_names, telling the agent where to obtain valid IDs, and it specifies ISO 8601 for the time bounds where the schema only says 'this time'. That is real meaning added over the schema.

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 verb and resource ('Count events') with a clear account-level scope, which cleanly separates it from siblings like count_matches, count_players, and count_progression_instances. The optional filter list further pins down exactly what is being counted.

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?

Explains how to narrow the count and explicitly states the no-filter default ('counts every event on record'), which tells an agent when an unfiltered call is appropriate. It lacks an explicit contrast with reporting alternatives such as get_event_report or aggregate_attribute, so the when-not guidance is only implied.

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