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

No annotations provided, so description must disclose behavior. It only states 'updates data' without explaining merge vs overwrite, error handling on non-existent email, idempotency, or return value. Minimal transparency.

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?

Extremely concise (one sentence), front-loads key info (verb, resource, fields). No fluff, but could benefit from structured formatting or bullet points for clarity.

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 6 parameters, no output schema, and no annotations, the description is severely lacking. It does not explain return value, error conditions, or behavioral nuances like partial updates.

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 0%, so description must compensate. It lists field categories (name, country, phone, tags) but omits specifics like first_name vs last_name, and does not mention email or provide details on format or constraints.

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?

Description clearly states the verb 'actualiza' (updates) and resource 'contacto existente' (existing contact), listing specific fields. It distinguishes from sibling create_subscriber (creates new) and get_subscriber (reads).

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 explicit guidance on when to use vs alternatives, prerequisites, or exclusions. Implied usage for updating existing subscribers but does not contrast with other tools like tag_subscribers or trigger_flow.

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