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

Annotations already declare it is a non-readonly, open-world, non-idempotent write. The description adds genuinely useful context beyond that: the plan gating that produces an upgrade message instead of a refresh, and the fact that it stores new snapshots. It stops short of noting cost/latency of fetching every source or whether snapshots append or replace, so not a full 5.

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 action, then the gating prerequisite, then the follow-up read. Every sentence carries distinct operational information with no padding.

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 zero-parameter action tool with no output schema, the description covers what it does, the prerequisite, the alternate return, and how to read results (get_trends). Nothing an agent needs to invoke 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?

The tool takes zero parameters, so there is nothing for the description to disambiguate and the baseline of 4 applies. No wasted or misleading parameter language.

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 states a specific verb and resource ('force a fresh fetch of trending hashtags from every trend source') plus the side effect ('store new snapshots'), which clearly separates it from read-only siblings like get_trends and get_trend_hooks. An agent can identify exactly what this does without opening the 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?

It gives the trigger ('instead of waiting for the scheduled refresh'), a prerequisite ('needs a plan that includes manual refresh'), the failure mode otherwise ('returns an upgrade message'), and the follow-up step ('use get_trends afterwards to read them'). When to use, the alternative it replaces, and the next call are all explicit.

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