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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the 'Read-only' claim adds little. What does add value is the statement of what the response contains (per-link totals and uniques, plus campaign-level counts) and the constraint that the campaign must have been sent, which hints at a failure or empty-result condition for drafts and scheduled campaigns.

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 sentences, zero filler, with the return payload front-loaded and the read-only/prerequisite caveats trailing. Nothing would be lost by keeping it exactly as written and nothing is redundant beyond the 'Read-only' restatement.

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 one required parameter, no output schema and full annotation coverage, the description supplies the missing piece – what the response looks like – which is the main gap a missing output schema creates. It stops short of covering empty-state behavior or how far back the per-link data goes, preventing a 5.

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% for the single parameter, and the schema's own description already says 'ID of a sent campaign (from list_campaigns)'. The description's 'campaign_id of a campaign that has been sent' restates the schema rather than adding format, sourcing, or error semantics, so the baseline of 3 applies.

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 description uses a specific verb and resource ('Show which links in a sent campaign were clicked') and enumerates the payload: total and unique clicks per link plus overall click counts. It is clear what the tool returns, but it never distinguishes itself from the very similar sibling get_campaign_clicks, leaving the agent to guess which one gives link-level detail.

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 via the prerequisite 'needs campaign_id of a campaign that has been sent', which tells the agent the campaign must already have been sent but not what to do otherwise. No alternative is named, and the overlapping get_campaign_clicks sibling is a real ambiguity the description should have resolved.

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