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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered. The description adds real behavioral value: sort order (by name), which events are included (all tracked names plus those with a currency), paging via next.starting_after, and the underlying endpoint.

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?

Dense and front-loaded: the resource and scope lead, then the identifier guidance, then paging, then the endpoint. Every clause earns its place with no filler.

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?

With no output schema, the description carries the return burden and does so reasonably: it describes what the list contains and its ordering, and fully explains paging. Minor gap is the exact shape of each returned record, but the essentials for correct invocation are present.

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 the baseline is 3. The description adds meaning beyond the schema by framing site_id/event identification and the paging cursor relationship (pass next.starting_after), clarifying the semantic role of ids within paging.

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 ('List a site's events') and clarifies the domain with '(conversions/goals)'. It distinguishes itself from siblings like fathom_get_aggregation by explaining that events are identified by name for use elsewhere, leaving no ambiguity about what this tool returns.

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?

Clearly routes the agent: identify events by name and use it as event_name in fathom_get_aggregation, and warns that the id is only a paging cursor. It gives positive context and an alternative relationship, though it does not state explicit when-not conditions for this list tool.

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