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

Annotations cover the safety profile (readOnly=false, destructive=false, idempotent=true), and the description adds genuinely non-obvious behavior: blocking is a visibility change that does not unfollow, and the operation is gated behind a preview/confirm_token handshake. It omits how the block is later removed, which is the one behavioral gap.

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 padding, with the effect of the call front-loaded ahead of the multi-step procedure. Every clause carries usable information.

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 mutation tool with no output schema, the description adequately explains the returned confirm_token and the required round-trip. The only missing piece is the reversal path (unblock_all_users), which an agent would need to reassure or later undo the action.

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 userId, username and confirm_token are already documented in the schema, including the preview-then-confirm protocol. The description restates that protocol but adds no syntax or constraint detail beyond what the schema provides, so the baseline 3 applies.

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 ('Block someone') and immediately defines the effect on the user's feed, Explore and Discover. It also distinguishes itself from the adjacent follow/unfollow siblings by explicitly noting it 'doesn't unfollow, like the app'.

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 explicit invocation context for the two-step flow: first call previews, repeat only after the user agrees. It contrasts with unfollow behavior, but never states when blocking is preferred over unfollowing or that unblock_all_users is the reversal path.

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