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

Annotations only declare readOnlyHint=true; the description goes well beyond that by disclosing the hard rate limit (2 calls per 60 seconds per API key), the pagination defaults (50, max 1000), and the date filter's default window. The rate-limit warning is exactly the kind of operational trait an agent needs to avoid throttling failures.

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?

Three short sentences, front-loaded with what the tool returns, then filters/paging, then the rate-limit caveat, closing with the raw endpoint mapping. Nothing is padded and the most decision-relevant facts come first.

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?

A read-only, six-parameter reporting tool with 100% schema coverage and no output schema; the description covers scope, types, paging, date filtering, defaults, and the rate-limit constraint. Nothing an agent needs in order to call this correctly is missing.

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 100%, so the baseline is 3; the description still adds value by supplying the page-size default of 50 (the schema only bounds it at 1-1000) and restating the type enum compactly. It stops short of clarifying the from/to default interaction beyond what the schema already says.

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+resource ('per-recipient activity for a campaign') and enumerates the exact activity types (Sent, Opened, LinkClicked, Unsubscribed, Bounced, Complained, Activity) the tool returns. This is specific enough to distinguish it from sibling reporting tools like get_campaign_summary or get_campaign_link_activity without opening a schema.

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 implied via the enumerated type values and the paging/date-filter notes, so an agent can infer this is the per-recipient detail endpoint. However, it never states when to prefer this over the obvious siblings (get_campaign_link_activity, get_campaign_activity_by_location, get_campaign_summary), which is a real missed routing cue given the overlapping 'LinkClicked' type.

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