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

Annotations already establish readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds substantive behavioral context beyond that: it details exactly what data surfaces back (per-network video file constraints, posting cadence, sourced 'from the network's own pages'), which an agent cannot infer from annotations alone.

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 with no filler. The primary scope is front-loaded, the returned detail follows, and the closing directive 'Read this instead of guessing a limit' is a compact, high-value call to action.

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 input schema, no output schema, and zero parameters, the description carries the full burden of explaining the return content — and it does so in detail (limits, media kinds, required fields, placements, video specs, cadence). Nothing an agent needs to decide to call 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 no parameter semantics are required and the baseline is 4. The description correctly spends no words on arguments and instead describes the returned payload.

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 a specific resource and scope: 'every network Mellow publishes to and the rules it enforces,' with a concrete enumeration of the rule families (caption limits, media counts, required fields, placements). It is clearly distinct from siblings like list_channels (the user's connected accounts) or validate_post, though it never explicitly names a sibling to contrast against.

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?

'Read this instead of guessing a limit' gives a clear condition for use: consult it before encoding platform constraints. It stops short of naming named alternatives (e.g. validate_post) or stating when not to use it, so it lacks true when/when-not routing.

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