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

Annotations already declare destructiveHint=true, idempotentHint=true, openWorldHint=true, and readOnlyHint=false, so the safety profile is known. The description adds genuinely new behavioral context: the action does not cancel a paid subscription and does not restore consumed invitations, scoping the side effects. It stops short of stating permissions or whether the action is reversible/re-followable.

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, zero waste, with the core action front-loaded and the caveats/routing following immediately. Every sentence earns its place.

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 an output schema present and rich annotations, the description needn't explain return values, and it covers side-effect scope plus sibling routing. A minor gap remains around permissions or reversibility of the unfollow, but nothing essential to invoking it correctly is missing.

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?

One parameter with 100% schema description coverage, including its source ('ID of a followed stream, from streams_following') and length bounds. The description adds nothing beyond the schema, which is the expected baseline when the schema does the heavy lifting.

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?

Specific verb (Unfollow) + resource (stream) + scope (for the signed-in account). It explicitly distinguishes itself from the sibling unfollow_user ('Use unfollow_user for authors'), so an agent can route without opening either 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?

Names the alternative tool and the condition that selects it (authors → unfollow_user), and clarifies the action's boundary (does not cancel a paid subscription). The when-to-use / when-to-use-something-else decision is fully covered.

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