List Codal letter types

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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so safety is covered. The description adds real behavioral context beyond them: the no-argument default behavior (returns 11 groups), the two-phase expansion via `category`, and the cross-tool contract that the returned `id` is the `letter_type` value for cd_search_letters. It stops short of describing the returned fields or ordering, which keeps it below a 5.

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?

Two tight sentences, front-loaded with the core purpose and followed by the operational recipe. Every clause carries actionable information; nothing is repeated from the schema or annotations.

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 single-optional-parameter read tool with no output schema, the description covers purpose, sequencing and downstream consumption. The remaining gap is the shape of the returned group/type objects (names, ids, counts), which the agent must discover by calling it.

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% with a 1-11 range already documented, so the baseline is 3. The description adds semantics the schema cannot: omitting the parameter changes the result set entirely (groups vs. types), and the returned ids are meant to be fed into another tool's `letter_type` parameter.

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 ('List codal.ir letter groups, or the letter types of one group') and explicitly ties the output to what the sibling cd_search_letters consumes. An agent can distinguish this lookup tool from cd_search_letters/cd_letter without opening any schema.

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 an explicit two-step procedure: call with no arguments for the 11 groups, then with `category` for that group's types, and names the downstream use of the returned `id` as `letter_type` in cd_search_letters. Both the when and the how are spelled out, with no alternatives left to inference.

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