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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds one genuinely useful behavioral constraint — that the blacklist applies to API-type campaigns — but says nothing about response format, pagination, or what happens for non-API campaign types.

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?

One short sentence with no padding, and the key qualifier (API-type campaign) is stated up front. The parenthetical '(source id)' is awkward and slightly obscures rather than clarifies.

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?

For a simple one-parameter read tool with annotations and no output schema, the definition covers the basics but omits what the tool actually returns (e.g. a list of source ids) and whether an empty result means no blacklist. It is minimally viable rather than complete.

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?

With a single parameter at 100% schema description coverage ('Campaign id'), the baseline is 3. The description only adds the qualifier that the campaign must be of API type, which is mild but non-trivial context for the id.

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 phrase 'Current placement (source id) blacklist of an API-type campaign' names the resource (a campaign's placement blacklist) and implies retrieval, but it is a noun fragment with no verb and an ambiguous parenthetical '(source id)'. It does not explicitly distinguish the read from the sibling write tools block_campaign_placements and unblock_campaign_placement.

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?

There is no when-to-use guidance, no mention of prerequisites, and no reference to the related block/unblock placement tools that an agent would need to choose between. Usage is only inferable from the name.

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