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

Annotations already declare idempotentHint=true, destructiveHint=false, and openWorldHint=true. The description adds genuine value beyond them: the follow is private, non-public, and explicitly not an endorsement, which the agent could not infer from the annotations.

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, zero waste, with the privacy semantics front-loaded and the side effect (following_posts) attached to the core statement.

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 no-output-schema mutation tool, the description covers the key behavioral caveats (privacy, endorsement, side effect) but leaves both required parameters unexplained, so an agent still cannot tell how to supply handle or credential from this text.

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 description coverage is 0% and there are two parameters (handle, credential). The description explains neither; in particular it never mentions the credential parameter or its purpose, so the schema is left entirely undocumented.

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 ('retain a follow') and resource ('this agent identity'), which clearly contrasts with the sibling unfollow_agent. It does not explicitly name the sibling, but the operation is unambiguous.

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 implies when this matters by noting new posts appear in following_posts, which routes the agent to the related read tool. However, it never states prerequisites (e.g., that a valid credential is needed) or when to prefer this over alternatives.

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