list_sources

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

With no annotations provided, the description carries the burden of disclosing behavior. It adds useful context: output size small (<2KB typical), no arguments, and cheap. This goes beyond a simple restatement of 'list' and helps set expectations, though it does not explicitly confirm side-effect-free behavior.

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 extremely concise: one main sentence followed by a short behavioral note. Every word earns its place, and the most critical information is front-loaded. There is no padding or redundancy.

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 zero-parameter tool with an output schema, the description provides sufficient context: what it lists, output size expectation, and cost. No return value explanation is needed given the output schema exists. It fully covers the necessary information in a simple, well-scoped tool.

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, and the input schema is empty (100% coverage). The description adds the explicit statement 'No arguments,' which reinforces the schema and is helpful for an agent deciding whether to invoke with parameters. Baseline for 0 params is 4.

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 clearly states 'List every data source currently loaded in this MCP session' with a specific verb and resource. This distinguishes it from sibling tools like describe_source or load_source, which have different purposes.

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 usage for a quick overview of loaded sources by mentioning 'No arguments. Cheap.' but does not explicitly state when to use this tool versus alternatives like describe_source or compare_sources. There are no exclusions or alternative tool references.

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