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

The readOnlyHint and openWorldHint annotations already establish that this is a safe, closed-world read. The description adds useful behavioral context by saying the guide is contained in one page and enumerating the integration stages covered, including Idempotency-Key, SAT errors, signed webhooks, cancellation, and production rollout.

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 first sentence front-loads the primary use case, and the second sentence compactly lists the covered topics. The bilingual repetition is slightly redundant but useful for a Spanish-facing API and does not obscure the main instruction.

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 zero parameters, no output schema, and annotations covering read-only/closed-world behavior, the description gives enough context for an agent to select this tool as the onboarding path. It could be stronger if it explicitly said what page or artifact is returned, but the core selection signal is present.

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 tool takes zero parameters, so there are no parameter semantics to document. Per the baseline for parameterless tools, a 4 is appropriate.

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 identifies a concrete starting-point guide for adding Fiscalisto / CFDI 4.0 invoicing to an app and summarizes the integration topics it covers. It is clearer than the generic name get_started, though it does not explicitly frame the tool as returning a documentation page.

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?

It gives a clear usage condition: start here when asked to add Fiscalisto or Mexican invoicing to an app. It does not state when not to use it or name sibling alternatives such as search_docs or get_page.

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