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

Annotations already declare destructiveHint=true, and the description's 'Destructive.' merely repeats that. It adds no information about permanence, whether the delete is idempotent, what happens when the contact is not found, or auth requirements — the API path is the only extra detail, and it is structural rather than behavioral.

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 clauses: action, safety flag, parameter rule, then endpoint. Front-loaded with the operation and zero filler; 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?

For a two-param destructive tool with no output schema, the essentials (what it does, that it is destructive, how to identify the target) are present. Missing is any behavior on failure or partial-success, which matters for an irreversible operation with optional parameters.

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 the baseline is 3, but the description adds a genuine constraint not present in the schema: the parameters are mutually exclusive identifiers ('email OR userId'). The schema has zero required fields and no oneOf, so this either/or semantics is real added value.

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 ('Deletes a contact from Loops') and is trivially distinguishable from siblings like loops_find_contact, loops_update_contact, and loops_create_contact. The added endpoint reference (POST /v1/contacts/delete) reinforces the exact operation.

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?

The description gives the identifying condition for calling it ('Supply email OR userId'), which is actionable, but never says when to prefer this over alternatives such as loops_find_contact (to verify before deleting) or how to handle a contact that may not exist. Usage is implied rather than framed.

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