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

The only behavioral trait disclosed is the upsert ('no duplicar'). With no annotations, more details like idempotency, field merging behavior, or error handling are needed. The description falls short.

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?

The description is a single sentence with no fluff, but it is too short for the tool's complexity. Conciseness is good, but structure suffers from omission of details.

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?

Given 7 parameters, upsert behavior, no output schema, and no annotations, the description is incomplete. It lacks return value info, conflict resolution specifics, and requirements beyond email.

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?

The description provides no parameter-level information. Only 57% of parameters have schema descriptions, and the description does not compensate for the missing ones (phone, first_name, last_name). It adds no value beyond the schema.

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 clearly states the tool performs an upsert (create or update) on a subscriber. The verb 'Crea o actualiza' and 'suscriptor' are specific. However, it does not explicitly contrast with sibling 'update_subscriber', which could cause minor ambiguity.

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?

No guidance is provided on when to use this tool versus alternatives like 'update_subscriber' or 'add_subscriber_to_list'. The implied usage (to create or update) is not sufficient for a clear decision.

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