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

Annotations already mark the operation as read-only, idempotent, and non-destructive. The description adds useful behavioral detail beyond annotations by specifying the output shape: 'Returns one SRC line per source' and enumerating the fields included. No contradictions exist.

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 efficiently state the resource, the fields, and the output format. There is no redundant padding, and the core action is front-loaded.

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 simple list tool with one optional parameter and no output schema, the description covers the returned fields and line format. It is nearly complete, though a brief note on the optional filtering behavior in the description itself would remove reliance on the schema.

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 schema has 100% description coverage for the only parameter, signal_type, including an example and an 'omit for all sources' note. The description adds no parameter syntax or format details beyond the schema, so the baseline of 3 is appropriate.

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 names a specific verb and resource: 'List the data-source endpoints feeding the wire,' and enumerates the returned attributes. This clearly distinguishes it from sibling tools like search_signals or list_facets, which concern signals and facets rather than data-source endpoints.

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 implies the tool lists all data sources, with the optional signal_type filter visible in the schema, but it does not explicitly state when to choose this over alternatives or when not to use it. Usage context is clear at a basic level, yet there are no exclusions or comparisons to siblings.

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