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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered. The description adds non-obvious behavior: for drafts it reports whether the chat app can still revise the draft and what remains outstanding, and it defines the null semantics of still_needed plus the review_link handoff for sending. That is genuine context beyond the annotations, though it does not describe error behavior for a missing id.

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, field list front-loaded, and the sibling pointer placed where it prevents a wrong call. The nested parenthetical about body.blocks/body.html is slightly dense but earns its place by linking the two tools.

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, the description carries the return-value burden and does it reasonably well by naming the fields returned and explaining the draft-state semantics. For a single-parameter read tool with full annotation coverage, only minor gaps remain, such as the response envelope and behavior when the id is unknown.

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, id, and schema coverage is 100% with a description ('The campaign's id.'), so the schema already does the work. The description adds no format, source, or lookup guidance for the id — baseline 3 is appropriate.

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 names the exact resource (one campaign) and enumerates what it returns — subject, preview text, sender, audience, and content — so an agent knows precisely what payload to expect. It also distinguishes itself from get_campaign_report ('Rates and top links are in get_campaign_report') and explains the relationship to create_campaign_draft's body.blocks, which a sibling name alone would not convey.

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 useful routing context — report metrics belong to get_campaign_report, and the content shape maps to create_campaign_draft's body.blocks/body.html — but no explicit statement of when to call this versus list_campaigns or update_campaign_draft. The draft-state guidance (still_needed null means ready, send from review_link) is workflow information rather than a use/don't-use rule.

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