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

Annotations already declare readOnlyHint=false, idempotentHint=true, destructiveHint=false. The description adds meaningful behavioral context beyond that: the platform executes the funding on the user's behalf (no manual transfer), the exact price point (0.01 USDC/query), and the downstream tool the funding unlocks. It does not address refundability, session expiry, or failure modes.

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?

Three short sentences, front-loaded with the core action and cost, with the routing hints packed in. The final telegraphic fragment ('Platform-executes funding so you can data_session_query') is dense but slightly awkward rather than wasteful.

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 one-parameter funding tool with no output schema, the description covers the action, the cost, the free alternative, and what it enables. Missing details are payment mechanics (escrow, refunds) and what happens if the session is already funded, but annotations cover the safety/idempotency profile.

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 the single session_id parameter is already documented as a UUID coming from data_session_open, so the description adds nothing new about parameters. Baseline 3 applies when the schema does the heavy lifting.

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?

Names a specific action (buy/fund per-query access to a live data listing) tied to a single session, and distinguishes itself from siblings data_preview (free trial) and data_session_query (post-funding consumption). An agent can pick this tool without opening any other 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?

Usage is clearly implied: use data_preview first for the free taste, fund here, then call data_session_query. The alternatives are named, but there is no explicit 'do not use this when...' or prerequisite statement (e.g., must already have opened a session via data_session_open).

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