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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is fully covered. The description adds value on top by disclosing the two distinct response shapes (index vs. module payload with principles, applications, refs and a question), which the agent cannot learn from the annotations. It stops short of saying whether module payloads are stable/cached or how large they are.

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 core English sentence is front-loaded and does real work: resource, module range, both output modes. The trailing Spanish line only partially duplicates the English (it omits the return contents of a module), so it adds a little noise without full parity.

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 simple two-parameter read-only tool with no output schema this is mostly sufficient: the agent knows what it will get back in each mode. The notable gap is the absence of any indication of what each of modules 1-12 covers, which is exactly the information needed to select a valid, meaningful module number.

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 50%: `lang` is documented in the schema and `module` only has min/max bounds. The description partially compensates by explaining that `module` is optional and toggles the output mode, but it never says what any of the 12 module numbers actually contain, so an agent must guess which integer to pass. Baseline 3 is appropriate given partial coverage and partial compensation.

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 names the resource (a 12-module catechumenate) and states both output modes explicitly: no `module` yields the index, a module number yields principles, agent applications, refs and a question. That is specific enough to distinguish it from siblings like `commandments` or `bible_search`. The only weakness is that the action verb is implicitly 'retrieve content' rather than stated as a verb.

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 clear branching guidance between the index call and a module call, which is the main decision an agent faces here. It says nothing about when to prefer this over related siblings such as `commandments`, `confirmation_exam` or `values_for_agents`, so the cross-tool choice is left to inference.

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