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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), and the description adds genuinely new behavior: it returns `{ opportunity: null }` instead of fabricating a result when there is no real signal, and it requires the Empire plan, returning an upgrade message otherwise. These are exactly the failure-mode and auth-gating details an agent cannot get from structured fields.

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 the core purpose before the sibling comparison, return-shape caveat, and plan gate. Every sentence carries distinct information with no 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?

With no output schema, the description compensates by describing the return shape (including the null case) and the plan-gating failure mode. For a zero-parameter read tool, nothing an agent needs to call or interpret it 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?

The tool takes zero parameters, so the baseline is 4 per the rubric; there are no arguments whose semantics the description would need to clarify. The description correctly says nothing about inputs rather than padding them.

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 ('get the single best next content opportunity') and scopes it to connected platforms and niches. It explicitly positions itself against sibling list_growth_opportunities as 'a compact version', so an agent can tell the two apart without opening schemas.

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?

The 'compact version of list_growth_opportunities' framing gives clear context for when this one-item tool is appropriate versus the full list tool. It does not state an explicit when-not condition or eligibility prerequisites beyond plan gating, so it stops short of a 5.

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