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

Annotations already declare destructiveHint=true, openWorldHint=true, and idempotentHint=false, so the safety profile is partly covered. The description adds genuinely useful context beyond that: the action is PUBLIC and should be user-confirmed, and undo reverses a follow into an unfollow. It does not reconcile the idempotencyKey retry story against the idempotentHint=false annotation.

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 compact sentences, front-loaded with the primary action and parameter, followed by a single high-value warning. No filler.

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 simple follow/unfollow tool with full schema coverage, no output schema requirement, and annotations covering safety, the description supplies everything an agent needs: the action, the inverse, the required identifier, and the public-confirmation caveat.

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 100%, so the schema already documents all four parameters, including undo and idempotencyKey. The description only lightly echoes targetUserId and the undo semantics without adding format or constraint detail beyond the schema, so 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?

States a specific verb and resource (follow an account on X) and names the required parameter targetUserId, plus the inverse operation via undo: true. An agent can distinguish it from siblings like bookmark_on_x or retweet_on_x at a glance.

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?

Gives clear usage context: this is the tool to follow, and unfollow is achieved by setting undo: true. It adds an explicit instruction to confirm with the user first because the action is public, but it does not name alternative/sibling tools or explicit when-not conditions.

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