Invoke a tool on a chosen server, spawning the server on first call. Ensure the tool exists by discovering available tools with get_server_tools first.
Call a tool on a specific server. The server is spawned on first call. The tool must exist on the server — use get_server_tools to discover first.
| Name | Required | Description | Default |
|---|---|---|---|
| tool | Yes | Tool name | |
| server | Yes | Server name | |
| arguments | No | Tool arguments as a JSON object. |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations are minimal (just readOnly and destructive hints), but the description adds behavioral context: the server is spawned on first call, and the tool must exist (implying failure if not). It doesn't disclose other behaviors like authentication requirements or side effects, but the annotations likely provide basic safety info. The description adds value but not exhaustive detail.
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 two sentences, concise and front-loaded with the primary action. The second sentence provides important usage guidance without wasting words. It's efficient but could be slightly more structured with explicit 'when to use' formatting.
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?
Given that it's a dynamic call tool with a nested object parameter, the description is decently complete. It mentions the need to discover tools, but does not describe return values or error handling. However, the lack of an output schema means it could do more, but the combination of schema and description is sufficient for an agent to proceed.
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 description coverage is 100%, so both parameters are already documented in the schema. The description adds little beyond that, such as the implication of the 'server' parameter being a server reference, but it doesn't add significant meaning beyond the schema. Hence, baseline 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 clearly states the tool calls a tool on a specific server, which is more specific than a generic 'call tool'. It also mentions the need for the tool to exist on the server, but doesn't explicitly differentiate from siblings like get_server_tools. Overall, it provides a clear verb and resource.
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 gives explicit usage guidance: use get_server_tools to discover tools before calling. It also implies that the server is spawned on first call, which is an important context. This is strong guidance for when to use this tool versus alternatives.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.