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

Annotations already declare destructiveHint=true, idempotentHint=true, readOnlyHint=false and openWorldHint=true, so the safety profile is covered. The description adds value beyond them by disclosing failure semantics ('Returns success=false when no follow exists or the operation fails'), which is non-obvious for an idempotent mutation. It stops short of stating permission/auth requirements or any rate limits.

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 short sentences, all front-loaded: purpose first, then failure behavior, then the disambiguation pointer. No filler and nothing that repeats the schema or title.

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 one-parameter destructive mutation with full annotations, an output schema, and 100% parameter coverage, the description covers purpose, failure semantics, and the nearest alternative. The only modest gap is that auth/permission requirements are only implied by 'signed-in user'.

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% and the single parameter is fully documented in the schema, including how to source the ID ('id from get_following_users'). The description adds nothing about userId, so the baseline 3 is appropriate when the schema carries the semantic load.

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 ('Stop following an author') plus the acting identity ('as the signed-in user'). It also names the sibling it is not (unfollow_stream), so an agent can distinguish it from the many other follow/unfollow and delete tools without opening a schema.

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?

Explicitly routes the agent: 'Use unfollow_stream to unfollow a stream' tells it when this tool is the wrong choice. It does not spell out prerequisites (e.g., must already follow, or how to obtain the userId), but the sibling routing is clear and actionable.

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