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

With no annotations, the description carries the full behavioral burden, and it is thin. It does not say whether the change persists in the project, whether it affects only the open editor or all editors, whether it is reversible via undo, or what happens if the language does not exist on the project despite the stated precondition.

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?

A single clean sentence with the core action front-loaded and the constraint trailing it. No filler, no restatement of the tool name.

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 mutation tool with no annotations, no output schema, and an undocumented parameter, the description leaves too much unstated: no failure behavior when the language is absent, no persistence or scope semantics, and no value format. It is a viable minimum but has clear gaps.

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 0% for the single required 'lang' parameter, so the description must compensate. It adds the constraint that the value must be a language already present on the project, which narrows the domain, but it never states the expected format (locale code such as 'en', display name, or ID), leaving the agent to guess the identifier shape.

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+resource pair ('Switch the open editor to a language'), scoped to the currently open editor, which is more precise than a bare 'set language'. It does not explicitly differentiate itself from the set_* siblings (set_device, set_resolution, set_template), but each targets a distinct setting, so an agent can place it easily.

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 phrase 'that already exists on the project' implies a precondition and a when-not condition (this tool will not create a new language), which is useful. However, no alternative tool or fallback path is named for the case where the desired language does not exist, so usage is only implied rather than spelled out.

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