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

With no annotations, the description steps up: it explicitly declares 'Read-only' and discloses a genuine data limitation (inbox vs spam placement is not reported by providers), which is real behavioral context an agent could otherwise get wrong. It omits freshness/caching behavior, which matters given the existence of a sibling sync_campaign_stats.

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?

It is front-loaded with the correct framing ('Email funnel:'), but the body is one very dense sentence stitched together with semicolons and em-dashes, reading as a metric dump. The content earns its place yet the structure hinders scanning.

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 and no annotations, the description must carry the return-shape burden, and it does enumerate funnel stages, delivery breakdown, and unique variant metrics thoroughly. The gaps are freshness of the numbers and whether the campaign must be active, which are not covered.

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?

There is exactly one parameter and schema description coverage is 100% ('Campaign id (UUID) from list_campaigns'), so the schema already carries full semantics. The description never mentions the id or its format, adding nothing beyond the structured field, which is the baseline-3 case.

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 name, title, and opening 'Email funnel:' make it clear this returns email performance metrics for a campaign, and the metric taxonomy (sent/delivered/opened/clicked/replied/bounced) is specific. Sibling disambiguation is implicit via 'email' versus get_campaign_linkedin_stats/get_campaign_phone_stats, but the description never explicitly distinguishes it from get_campaign_analytics or get_campaign_email.

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?

No sentence says when to use this versus alternatives such as get_campaign_analytics, get_campaign_email, get_campaign_live_status, or sync_campaign_stats. Usage is only implied by the tool name and the returned-metric list, which leaves the agent to infer routing.

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