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

With no annotations provided, the description carries the full burden of behavioral disclosure. It states that the tool 'returns' the result, implying a read-only operation with no side effects. It also discloses a financial aspect ('Free once the contract is yours') and a security feature (Sphere's signature) that adds trust verification. It does not explicitly state 'does not modify anything,' but the language strongly implies a non-destructive get. It also specifies a precondition (status=delivered), which is useful behavioral context. This goes beyond a minimal statement of purpose.

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 a compact paragraph that front-loads the primary purpose ('Verify what you bought') and then explains the output, usage timing, and requirements. It avoids redundancy and includes only relevant details. It is slightly longer than strictly necessary but each sentence contributes value—purpose, output, usage order, and prerequisites. The structure is logical and efficient.

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 simple three-parameter tool with no output schema, the description covers the essential aspects: what it returns (delivered result, contract hash, signature), when to call it (after status=delivered), and what prerequisites exist (agent_id, api_key, contract_id). It also mentions the purpose (verification) and cost (free after ownership). While it doesn't describe error handling or edge cases (e.g., what if contract not yet delivered), the precondition 'status=delivered' implies that it should be called only then. Given the tool's simplicity and the absence of an output schema, this is a complete enough description for an agent to use 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?

The schema has zero description coverage, so the description must explain the parameters. It explicitly mentions all three required parameters: 'Requires agent_id + api_key (from marketplace_register) and contract_id.' It clarifies the source of api_key (from marketplace_register) and implies that contract_id identifies the specific contract whose result is being fetched. This adds meaning beyond the bare parameter names, though it doesn't provide formats or validation rules. It adequately compensates for the schema's lack of descriptions.

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's purpose: 'Verify what you bought: returns the delivered result of one of your contracts together with its contract hash and Sphere's signature.' It names a specific verb ('verify', 'returns') and resource ('delivered result of one of your contracts'), and it distinguishes itself from siblings like marketplace_get_contract (which presumably returns contract metadata) by focusing on the delivered result and verification artifacts. The purpose is unambiguous and unique among the listed siblings.

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 sequencing: 'Call after status=delivered, then marketplace_complete_contract to release payment.' This gives a clear when-to-use condition and the order relative to other marketplace tools. It also notes 'Free once the contract is yours,' implying ownership as a prerequisite. While it doesn't explicitly list alternatives or say 'use this instead of X,' the timing and context are clear enough for an agent to decide when to invoke it.

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