federation_call

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

Beyond the annotations (readOnlyHint=false, openWorldHint=true, destructiveHint=false), the description discloses that results are scanned and sandwich-wrapped if flagged, and that this is an egress lane requiring a lease. It also mentions that the capability allows spawning a server at all. This adds meaningful behavioral context about side effects and output handling that annotations alone do not provide.

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 paragraphs with zero filler. The primary purpose is front-loaded in the first sentence, followed by necessary security context and output handling. Every sentence earns its place; no word is wasted.

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 complex federation tool with no output schema, the description covers authorization and output sanitization thoroughly but omits parameter semantics, return details, and error behavior. Given the tool's high complexity and the absence of output schema, the lack of parameter explanation and return type description makes it incomplete, though the security aspects are well addressed.

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 0%, so the description must compensate for parameter meaning, but it does not. The description implies server_id and tool through its opening statement, but app_id and arguments are entirely unexplained. The schema itself only provides generic titles and type names, leaving the agent to guess that app_id identifies the calling app and arguments are passed to the downstream tool. This is insufficient compensation.

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 opens with 'Call one tool on one ratified downstream MCP server,' which states a specific verb (call), resource (one tool on a specific server), and scope (ratified downstream MCP server). It clearly separates this from sibling tools like federation_list_servers (which lists servers) and integration_call (which calls integrations). No ambiguity exists.

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 explicit and detailed authorization prerequisites (manifest capabilities, namespace permission, operator consent, egress lease, ratified registry), giving clear when-to-use context. However, it does not explicitly mention alternatives, exclusions, or when not to use this tool. It implies this is the general call tool but doesn't contrast with federation_discover or federation_list_servers, so it stops short of a full 5.

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