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

Annotations already cover idempotency and non-destructiveness. The description adds that this is a test-only check rather than a save operation, and the config parameter notes that credentials are encrypted at rest and never returned by read tools. It does not describe the result/return format, but this is partially mitigated by the annotations.

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 sentences with no filler. The first sentence front-loads the core purpose, and the second sentence efficiently lays out the two invocation modes. Every clause earns its place.

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?

The description covers the main branching logic and safety characteristics needed to invoke the tool correctly. The lack of an output schema means the return format is not described, but for a simple connectivity test the success/failure semantics are reasonably inferable from 'Check whether... works.'

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%, so the baseline is 3. The description adds meaningful parameter relationship semantics: pass an existing dataSourceId to retest a saved connection, or pass type and config to test new settings. This clarifies the mutually exclusive use cases beyond what the individual property descriptions provide.

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 and resource: 'Check whether a set of connection settings actually works, before saving them.' It also distinguishes the tool from add/update/list operations by emphasizing pre-save validation and by describing both retesting an existing dataSourceId and testing new type/config settings.

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 description provides clear usage context: use this tool before persisting connection settings, and choose between retesting a saved connection with dataSourceId or testing new settings with type+config. It does not explicitly name sibling alternatives, but 'before saving them' implies it should precede add_data_source or update_data_source.

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