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

The description discloses key behavioral traits beyond the sparse annotations: each query costs 0.01 USDC, there is a maximum of 20 queries per session, and the operation requires a prepaid/funded session. This meaningfully augments the readOnlyHint/idempotentHint/idempotentHint annotations, though it doesn't address retries, failures, or refund behavior.

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 and every sentence carries weight: purpose, pricing/quotas, free alternative, and required setup sequence. It avoids filler and front-loads the core action.

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 description supplies essential operational context like pricing, quota, and sequence, but with no output schema and 40% schema coverage, it still lacks a full picture. An agent is left guessing at return format and the semantics of several parameters, so the description is minimally adequate rather than 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 adds little for the undocumented parameters. It doesn't explain what 'query' should contain, what 'k' represents, or how 'delivery_receipt' works. The phrase 'REST body + session id' is too vague to compensate for the missing parameter context.

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 function: 'Buy per-query access to live data listings' and 'Run a prepaid query against a funded data session.' It also distinguishes itself from related siblings by naming the exact sequence (data_session_open → data_session_fund → data_session_query) and highlighting data_preview as the free alternative.

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 preconditions and sequencing: it must follow data_session_open and data_session_fund. It also identifies data_preview as the free first-taste alternative, guiding the agent on when to consider that sibling tool. This is actionable and leaves little room for misrouting.

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