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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds real context beyond them: newest-first ordering, 20-per-page pagination, the fact that DELETED campaigns never appear (so deletion looks like disappearance), and the owner-only constraint on userId. That is exactly the extra behavioral detail annotations cannot carry.

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?

Dense but front-loaded: scope and ordering first, then filter semantics, then the deletion caveat, then sibling routing, then the permission note. No sentence is filler.

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?

No output schema exists, and the description compensates by telling the agent the return shape is a partial list ('a few fields each') and pointing to campaign_get for full detail. Combined with pagination and permission notes, nothing needed to call it 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 coverage is 100%, so the baseline is 3, but the description adds meaning the schema does not: the practical distinction between DRAFTED and ACTIVE statuses and the permission rule for userId. It stops short of covering page/keyword semantics, which the schema already handles.

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 and resource ('Campaigns in your account') plus ordering and page size, and explicitly distinguishes itself from campaign_get and analytics_campaign. An agent can tell it apart from siblings 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?

Names the alternatives and the condition that selects them: 'for one campaign in full use campaign_get, and for performance analytics_campaign.' It also explains what the status filter means in practice (DRAFTED = being built, ACTIVE = sending now).

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