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

Beyond the supplied readOnlyHint/destructiveHint, the description discloses the key behavioral contract: ids are stable across polls, and new items arrive on top so consumers must dedupe. It also discloses retention differences per event family (History-backed events versus match.needs_review, whose id changes when flagged again), which directly affects polling logic.

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?

Front-loaded with the one-line purpose, then a poll/dedupe paragraph, then two scoped bullet lists for event families and item payloads. Every section is load-bearing, though "what an automation needs, with no second call" is slightly promotional phrasing rather than specification.

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-value burden and mostly discharges it: item id stability, null contact fields after deletion/merge, absorbed-contact ids, and account attention reasons. It stops short of naming the concrete payload fields or the response envelope, leaving the exact shape partly unspecified for a tool an automation will parse.

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, but the description adds real meaning beyond the enum descriptions: retention lifetime for History-sourced events and the id-instability of match.needs_review. It says nothing extra about limit or cursor beyond what the schema already documents.

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?

"Lists the events of one type, newest first" gives a specific verb, resource and ordering in the first sentence, and the polling-automation framing makes the tool's role unmistakable. None of the siblings (contact_*, sync_start, api_key_check) overlap with event retrieval, so the agent can route here without ambiguity.

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?

It states the intended usage pattern concretely: poll repeatedly, keep the ids you have seen, skip the rest, and use cursor to read further back. It does not name a when-not-to-use case or point at an alternative tool for other needs, which keeps it 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.