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

Annotations already declare readOnlyHint=false, idempotentHint=true and destructiveHint=false. The description adds genuinely new behavioral context beyond those: the cost (0.01 USDC/query) and that the platform itself executes the funding on the buyer's behalf. It omits failure/refund behavior, so it is useful but not complete.

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 short and front-loads the core action, but the hardcoded 'applenewswatch: Official Apple Newsroom Announcements' example reads as noise or a snapshot that does not belong in a general tool description, and the sentence structure is slightly fragmented.

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 single-parameter action with no output schema, the description covers the preconditions (a session from data_session_open), the cost, the payment mechanism, and the follow-up step (data_session_query). Only edge cases like funding failures or balance insufficiency are 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?

There is a single session_id parameter with 100% schema description coverage and an explicit note that it comes from data_session_open. The description adds no syntax or format detail beyond the schema, so the baseline of 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 states a specific action (fund/buy per-query access) on a specific resource (an existing buyer data session) and names the sibling tools that bracket it (data_preview before, data_session_query after). An agent can distinguish it from data_session_funding_package or data_session_query, though the embedded hardcoded listing detail slightly muddies the core 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?

It gives a clear workflow context: preview free first via data_preview, then fund so you can data_session_query. It does not explicitly state when NOT to use it or how it differs from data_session_attach_escrow / data_session_funding_package, so it stops short of full routing guidance.

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