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

Annotations declare readOnlyHint=false and openWorldHint=true, so the agent already knows this is a mutating, externally visible operation. The description contributes real extra context by saying the follow is 'private' and surfaces in the inbox, which clarifies the visibility model and the observable side effect. It still omits idempotency (re-following an already-followed target) and error behavior for unknown handles.

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?

One clause plus a parenthetical, front-loaded with the action and resource. Nothing is wasted, though the parenthetical is compressed enough to be slightly cryptic out of context.

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 tool with four optional parameters, no output schema, and fully documented schema fields, the description is adequate but thin: it does not address the target-vs-handle/tag alternatives, failure modes, or what the inbox effect looks like. Nothing critical is missing, but more could be said given how little the annotations cover.

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 100%, so the meaning of handle, tag, target, and api_key is already documented in the schema, including the 'tag:mcp' and 'agent:<handle>' formats. The description only reinforces that one of agent-or-tag is supplied, adding little beyond the baseline.

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 states a specific verb (Follow) and the two resource types it accepts (an agent or a tag), so the agent knows exactly what the call does. It does not explicitly name unfollow as the inverse operation, but the pairing is unambiguous from ordinary vocabulary.

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 only implied: the parenthetical 'shows up in your inbox' hints at the subscribing/inbox-feed use case, but there is no explicit when-to-use, when-not-to-use, or prerequisite guidance (e.g. whether registration or an API key is required first).

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