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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds genuinely new behavioral facts: it never fabricates results (returns an empty list when no real signal exists) and it is entitlement-gated to the Empire plan, returning an upgrade message otherwise. Those failure modes and access constraints are exactly what annotations cannot express.

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 sentences, no filler, and the actual capability is front-loaded before the failure mode and the plan gate. Every sentence carries distinct information.

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 naming the returned fields (hashtag, growth, posting suggestion, empty-list guarantee), and with annotations covering safety it adds the plan gate. There is no parameter surface left unexplained, so an agent can call this confidently.

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 of 4 applies. The description correctly adds no parameter text, and instead explains the implicit inputs (user's niches, connected platforms) that filter the output, which is useful framing rather than schema repetition.

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 gives a specific verb and resource ("List rising trends worth posting about now") plus the scoping constraints (user's niches, connected platforms) and the payload of each item (hashtag, growth, posting suggestion). That is enough to separate it from get_next_growth_opportunity and get_trend_hooks, though it never names a sibling outright.

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 by "worth posting about now" and the niche/platform restriction, but there is no explicit when-to-use vs when-not, and no mention of the obvious alternatives (get_trends, get_trend_hooks, get_next_growth_opportunity). The plan requirement is stated, which is a prerequisite rather than selection guidance.

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