Add an opt-out

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

Annotations already cover the safety profile (readOnlyHint=false, idempotentHint=true, destructiveHint=true). The description adds real value beyond them by disclosing the environment-flag prerequisite (VOBIZ_ENABLE_MESSAGING=true) and the confirm gate, and by restating the idempotency guarantee in plain terms ('Safe to repeat'). It does not mention how the block is reversed or any permission model, which keeps it at a 4.

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, front-loaded with the action and effect, followed by prerequisites and the idempotency note. No filler or redundancy.

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 4-parameter mutation with no output schema, the description covers effect, example trigger, prerequisites, and repeat-safety. The only meaningful omission is how to undo the block, though the sibling remove_opt_out partially signals that.

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 75%, so the schema already documents reason, channel, and confirm well. The description only restates the confirm requirement and implies channel scoping without adding format or syntax detail, so it adds little beyond the structured fields.

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 and resource: 'Block a phone number from receiving messages on a channel.' That phrasing distinguishes it cleanly from the sibling check_opt_out (query), list_opt_outs (enumerate), and remove_opt_out (reverse), without needing to open any 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?

It gives a concrete usage context ('for example after a customer asks to stop') and a hard precondition (confirm: true), so the agent knows when this tool is appropriate. It stops short of explicitly naming the alternatives or stating when NOT to use it, so it falls just short of a 5.

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