Backend Capabilities

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

With readOnlyHint=true already present in annotations, the description adds only marginal behavioral context: the result is 'machine-readable' and scoped to the 'active backend'. No side effects or additional behavioral traits are disclosed, but there is no contradiction.

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, front-loaded sentence that directly states the action and resource. Every word earns its place with no redundancy or filler.

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 no-parameter, read-only introspection tool with an output schema present, the description is fully sufficient. An agent can invoke this tool immediately without missing prerequisites or needing to understand return-value details, since the output schema covers that.

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 has zero parameters, so the description carries no parameter burden. Baseline 4 is appropriate because no parameter semantics are needed and the schema confirms there are no inputs.

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 states a specific verb ('Return') and a distinct resource ('machine-readable support modes for the active backend'). It clearly separates this from sibling tools like system_status or system_about, which concern status or general information rather than capability/support-mode discovery.

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 'for the active backend' gives clear context that this is for discovering what the current backend supports, and no exclusions or alternative tools are needed for a zero-parameter introspection call. It lacks explicit when-not-to-use guidance, but the context is sufficiently clear.

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