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

Annotations only declare readOnlyHint=false, destructiveHint=false and openWorldHint=true; the description adds the substantive behaviour the agent actually needs — login is required, official agents and free twins activate immediately, paid twins return a Stripe checkout URL, and the call may settle in a "pending" state. Missing is what happens on a repeat hire or whether the entitlement can be undone, but the purchase-flow disclosure is well beyond annotation coverage.

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 behavioural sentence is front-loaded before the Args/Returns blocks, and every line carries information. The docstring-style Args section partially restates the schema property names, which is mild redundancy, but the total length is proportionate to a two-parameter tool.

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?

There is no output schema, so the description compensates by spelling out the return shape including the optional checkout_url and the active/pending status. Combined with the login prerequisite and payment branch, an agent has enough to call this correctly and interpret the result; only edge behaviour such as re-hire idempotency is unaddressed.

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 carries the burden, and it does: slug is tied to "the marketplace listing" (telling the agent where the value comes from), and api_key is described as a bearer token marked required. It stops short of format examples or what happens when api_key is omitted despite the schema default of empty string.

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?

"Hire a marketplace agent" is a specific verb plus resource, and the parenthetical login requirement sets it apart from read-only siblings like awareness_agent_detail or awareness_find_agents. It does not explicitly contrast with awareness_run_agent_task or awareness_chat_agent, which are the nearest neighbours for 'using' an agent, so the sibling differentiation is implicit rather than stated.

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?

"Use this after the user has tried an agent and wants to keep using it" gives a concrete triggering condition and a clear antecedent (trial, then hire). There is no explicit when-not or statement about what to do if the agent is already hired, but the sequencing guidance is strong enough that an agent knows when to reach for this tool.

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