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

Annotations already establish readOnlyHint=false and destructiveHint=false, so the description adds useful behavioral context by disclosing the per-query charge of 0.01 USDC and the 20-query session limit. This tells the agent that invoking the tool consumes prepaid balance and is bounded per session, which goes beyond the annotations.

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 compact, front-loaded with the core purpose, and every clause adds relevant context: free preview alternative, the specific listing, pricing, session limits, and the required call sequence. It avoids verbose phrasing or redundant restatement of the schema.

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?

The definition captures the high-level flow, cost, and session constraints well, but leaves gaps for an agent trying to invoke it correctly: k and delivery_receipt semantics are unclear, and there is no guidance on failure behavior such as insufficient funds or expired sessions. Given the absence of an output schema, a bit more parameter and error context would make it fully complete.

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 only 40%, and the description does not compensate for the undocumented parameters. k, delivery_receipt, and query are not explained outside the schema, and query only has generic min/max length constraints. The description's cost and sequence details do not clarify what values these parameters should take.

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 schema description explicitly states 'Run a prepaid query against a funded data session,' which names the verb, resource, and precondition. The sequence data_session_open → data_session_fund → data_session_query also clearly positions this tool relative to its siblings, and the annotation title 'Query Data Session' reinforces the purpose.

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 gives an explicit ordered sequence for when to use this tool and names data_preview as the free first-taste alternative. It also communicates per-query cost and a 20-query session cap, so an agent understands this tool is intended for paid, prepaid querying after funding.

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