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

Annotations already declare readOnly, idempotent, non-destructive and openWorldHint=false, so the safety profile is covered. The description adds genuinely new behavioral context: free tools need no sign-in while paid tools incur per-use charges, and a hard anti-hallucination constraint. The return-field sentence is somewhat redundant given the output schema exists, which keeps this from a 5.

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?

Four sentences, front-loaded with the action and the free/paid split, then usage trigger, then return shape, then guardrail — a sensible priority order with little waste. The 'Returns name, one-line summary, price, actions and offeringUrl' sentence partially duplicates the output schema and is the one element that could be trimmed.

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 search tool with an output schema and full annotation coverage, the definition supplies everything an agent still needs: the trigger condition, examples, the free-vs-paid decision that determines the next call, and explicit fallback behavior. Nothing material to correct invocation is missing.

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 100% and all four parameters carry their own descriptions and enum values, so the schema does the heavy lifting. The description's free/paid framing loosely maps to the 'access' filter but adds no syntax, defaults, or interaction details beyond what the schema already states. Baseline 3 applies.

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 a specific verb and resource ('Search the Vybe Marketplace for MCP tools') and immediately partitions the result space into free vs paid, naming the sibling that consumes each kind (run_free_tool, pay_offering). An agent can distinguish this from get_tool or run_free_tool 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?

It states the triggering condition explicitly ('when the user asks for a capability you do not have'), gives three concrete examples (PDF, postcode, crypto transaction), and supplies a fallback rule ('Never invent tools; if nothing fits, say so'). The 'Related: get_tool, pay_offering' line further routes follow-up calls.

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