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

With no annotations, the description carries the full burden and does so richly: it discloses that counters can lag a few minutes behind get_campaign_stats, enumerates exactly which fields return null and why (null = not measured), explains audience_count timing/audience_basis, and states null semantics rather than invented zeros. This is a substantial behavioral disclosure beyond any structured field.

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 content is relevant and front-loaded with the tool's purpose, and every clause about metric definitions earns its place given there is no output schema. However, it is one very dense, uninterrupted paragraph with no structure, making it hard to scan for an agent that only needs the purpose and status filter.

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?

There is no output schema, so the description must explain return values, and it does so thoroughly: it defines enviados, entregados, abrieron, clics únicos, the rate denominators (rate_base "delivered"), and flags *_fraction as deprecated. Nothing needed to interpret the response is missing.

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 real value the schema lacks: the enumerated status values (draft, scheduled, sending, sent) for a parameter whose schema has no enum. It does not elaborate on limit semantics beyond the schema's "1-500, default 20".

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 ("Lista las campañas/correos del tenant con sus métricas") and immediately scopes what it returns. It distinguishes itself from get_campaign_stats and get_campaign_audience by naming them and stating which data belongs to which, so an agent can tell the three apart.

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 explicit routing to alternatives: the null counter fields must be requested from get_campaign_stats, and the exact net audience from get_campaign_audience. It also documents the status filter values. It lacks an explicit "use this when you want to enumerate campaigns" statement or any exclusions, so it stops short of a full 5.

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