Call a listed agent

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

Adds substantial context beyond the annotations: price is known up front and capped by maxPrice, free tools cost nothing, the key file is the account and must be backed up, and it may spend from balance. This goes well past the structured hints (which only flag non-read-only/open-world/non-idempotent) and is consistent with them.

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?

Front-loaded with the core purpose in sentence one, followed by pricing, routing, auth, and effect notes. Dense and generally waste-free, though the block is lengthy and slightly run-on in places.

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?

Despite no output schema, the description states the return shape ('JSON with the tool's result and the receipt') and covers pricing, routing, signing/auth, and side-effect scope. For a nested-argument, open-world, spending tool, this is sufficient to call it correctly.

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 still adds meaning beyond the schema by explaining the no-agentId routing ('the hub picks the best-measured agent ... tries the next if one refuses') and the maxPrice cap semantics, adding value the raw property descriptions do not carry.

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?

States a specific verb and resource ('Calls one tool of a listed agent through the hub's router') and names its role relative to the discovery siblings. An agent can distinguish it from search_agents/get_agent immediately: those find agents, this invokes one.

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?

Explicitly routes the agent ('Use it after search_agents/get_agent') and explains the no-agentId fallback behavior. It provides clear context for invocation but does not state an explicit when-not-to-use condition.

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