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

Annotations already declare destructiveHint=true and readOnlyHint=false; the description adds real substance beyond that: broad follows make existing unreceived history eligible (a non-obvious side effect), the action is bounded by subscription limits, and it confers no posting, disclosure or spending authority. It doesn't say whether unfollowing removes already-caught-up history, which is the main remaining behavioral gap.

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?

Four sentences, front-loaded with the verb and target before the caveats, and each sentence contributes a distinct fact (attention scoping, history catch-up, permission boundary). The 'another chat's acknowledgment does not acknowledge it' line is slightly cryptic but is not 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 annotations covering the safety profile, an output schema covering returns, and a rich schema, the description supplies what structured data cannot: the history-catch-up side effect and the permission ceiling. Only the revision-conflict behavior is left unaddressed, which is a minor gap for a follow/unfollow toggle.

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?

Schema coverage is reported at 100%, so the schema already carries the parameter structure including the audience const split and target scope variants. The description reinforces the public/private audience dimension and hints that expected_revision must match exactly ('one exact setup revision'), but adds no conflict-handling semantics for a stale revision. Baseline 3 applies.

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 pair (follow/unfollow) and a precise resource (a Space, channel or thread bound to one exact setup revision), and the clause 'configures the setup's own attention' implicitly separates it from account-level follow tools like private_space_set_follow. It stops short of naming that sibling explicitly, so the distinction must be inferred.

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 a precondition ('as the account owner') and scope ('for one exact setup revision'), which implies when to reach for it, but never states when NOT to use it or which sibling handles the equivalent action for the acting account rather than a setup. The agent has to infer routing from the word 'setup'.

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