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

With no annotations, the description must carry the behavioral burden, and it does disclose several non-obvious traits: the delivery is gated by Sphere before the buyer sees it, it is free, and it requires auth credentials. It stops short of covering what happens if the gate fails, retry/idempotency, or reversibility.

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 seller-vs-buyer distinction is front-loaded, and the remaining clauses cover gating, cost, and required inputs with no filler. Every sentence earns its place.

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 mutating tool with a nested object parameter, no annotations, and no output schema, the description covers purpose, auth, cost, and gating well but omits the failure path (gate rejection behavior), return shape, and result_payload contents. Adequate but with clear gaps.

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 0%, so the description is the only source and it names all four parameters and clarifies that api_key comes from marketplace_register. However, it does not describe the structure of the nested result_payload object or the format of contract_id, leaving the highest-ambiguity parameter undocumented.

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 (deliver) and resource (the result for a contract you accepted), and explicitly marks the scope as the seller path rather than a buyer step. An agent can distinguish it from buyer siblings and from contract lifecycle siblings without opening any schema.

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?

"Seller path -- not a buyer step" plus "the result for a contract you accepted" give a clear precondition for when to call it. It does not, however, explicitly disambiguate against marketplace_complete_contract, which is the most likely confusion among siblings.

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