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

Annotations already establish readOnly, non-destructive and closed-world, so the safety profile is covered. The description adds genuine value beyond that by disclosing the actual detection logic and by warning that the output is probabilistic signals with evidence rather than a verdict of abuse, which shapes how an agent should report results.

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?

Two tight sentences: the detection behavior is front-loaded, then the interpretive caveat. Nothing is redundant, though the heuristic list is somewhat compressed and could be slightly more scannable.

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 is the only place the agent could learn what comes back, and 'reports signals with evidence' is vague about structure and thresholds. The detection logic is well covered, but the two tuning parameters and the result shape remain under-explained for a tool whose output drives abuse judgments.

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 0% for both parameters, so the description must carry the burden and it largely does not: window_hours and baseline_days are never mentioned. 'Recent signups' and 'the usual hourly rate' only hint that a lookback and a baseline exist, without clarifying the distinction between the evaluation window and the comparison period, or their defaults and caps.

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 concrete verb and resource ('compares recent signups... looks for spikes') and enumerates the specific detection heuristics: hourly-rate spikes, many accounts from one non-consumer email domain, and sub-minute bursts. That is enough to distinguish it from siblings like get_recent_signups (raw listing) and detect_api_abuse (different surface), though it never names those siblings explicitly.

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?

Usage is only implied by the word 'detect' and the closing caveat that results are 'signals with evidence, not proof of abuse,' which usefully frames how to act on output. There is no explicit when-to-use statement, no mention of when to prefer get_recent_signups or find_users_at_risk, and no prerequisites or follow-up guidance.

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