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

Adds substantial context beyond the annotations: the opt-out list is shared across accounts, so removal is restricted by ownership, and the call reports one of three outcomes (lifted, never there, belongs to another account). This fills in the failure semantics that destructiveHint alone does not convey. It does not discuss irreversible side effects beyond removal itself, but that is a minor 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?

Three well-formed sentences, front-loaded with the action before the precondition and the outcome reporting. Slightly overlaps with the schema's parameter description but no sentence is wasted.

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 single-parameter mutation with no output schema, the description covers purpose, precondition, and return outcomes — exactly the information an agent cannot get from structured fields.

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 schema already documents the single contact parameter, including accepted formats and the ownership restriction. The description adds only marginal scope framing, 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 ('Take a contact off this account's opt-out list') with explicit scope — this account's list, not the shared list. An agent can distinguish it from add_opt_out 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?

Gives concrete triggering conditions: a record added by mistake, or a person who asked to be contacted again, plus the hard precondition that only records this account created can be lifted. It does not explicitly name add_opt_out as the inverse operation, but the context is unambiguous.

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