Does a principal follow this handle? (free)

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

Annotations already cover readOnly/destructive/openWorld, so the bar is lower; the description still adds real semantics: the special status value 'already_following_when_tracking_began', the NULL followed_at for pre-tracking edges, and the explicit guarantee that RobinX never fabricates an unwitnessed follow date. That is exactly the kind of data-integrity behavior an agent needs to interpret results. It does not address rate limits, auth, or pagination, so not a 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 sentences, front-loaded with what is returned, then the caveat, then the cost tier. No filler. The first sentence is dense but carries the full payload rather than 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?

With no output schema, the description takes on return-value explanation and does so reasonably: it outlines that results are principal accounts, a since-date, and follow/unfollow history, and defines the edge-case status. It leaves the concrete response shape (list vs object, how principals are identified) unspecified, which is a modest gap for a free lookup tool.

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 a single parameter with 100% schema description coverage ('X handle, with or without @'), so the schema already does the work. The description adds no format, casing, or resolution detail beyond the schema. 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 a specific verb+resource: which watched Robinhood Chain principal accounts follow a given X handle, plus since when and follow/unfollow history. That is a concrete, distinctive query direction (principals → handle) that an agent can distinguish from the sibling robinx_follows without opening either schema. It stops short of explicitly naming the reverse-direction sibling, so differentiation is inferable rather than stated.

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 the framing — this answers a who-follows-whom question over tracked principals, and 'Free' signals a cost tier against paid siblings. There is no explicit when-to-use, when-not-to-use, or named alternative (e.g. robinx_follows for the opposite direction), so the agent must infer routing.

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