geo_get_region

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

There are no annotations, so the description carries the full burden. It does disclose the core behavior: the tool retrieves and returns one region by code, and it adds that the code is an 'Official region code.' It does not mention what happens for unknown or malformed codes, or any other edge behavior, but for a simple read-style getter the disclosed behavior is adequate though incomplete.

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 description is two sentences, front-loaded with the core action, and includes only the one parameter explanation that matters. There is no filler or repetition of the tool name beyond the docstring-style parameter label.

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-parameter lookup with an output schema, the description is nearly complete: it states what is returned, by what key, and gives an example. The main missing context is routing guidance toward the sibling search tool and clarifying not-found behavior, but these are minor for a simple getter.

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 input schema only declares that code is a string with no description, so the description adds meaningful value by calling it an official region code and giving the concrete example '11' for Île-de-France. With only one parameter and a degenerate schema, this is strong compensation for the 0% schema coverage.

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 uses a specific verb and resource combination: 'Return one region by code.' It is clearly distinguished from sibling geo_search_regions, which implies searching multiple regions, because this tool fetches a single region by an official code. For a simple getter this is exactly the level of specificity an agent needs.

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?

The intended usage is implied rather than explicit: it is appropriate when a region code is known and exactly one region is wanted. However, the description does not mention the alternative geo_search_regions or state when not to use this tool, so the agent must infer the decision boundary.

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