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

Annotations already signal this is not a read-only or idempotent operation. The description adds useful behavioral context: it is a paid, per-query session with a cost of 0.01 USDC/query and a session cap of 20 queries. However, it does not disclose side effects such as escrow requirements, what happens on open, or what the response contains, which matters because there is no output schema.

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-loaded with the core purpose, but the 'Listing: bleepingwatch...' sentence is ambiguous: without an 'e.g.' it may be mistaken for a required or only supported listing. The workflow sentence 'Open a prepaid session, then fund and query' is concise but underspecified. Overall it is compact, yet the ambiguity reduces its structural quality.

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?

This is a payment- and session-related tool with 6 optional-looking parameters, no output schema, and 50% schema description coverage. The description fails to explain how to identify a listing generally, what open_tx_hash and proof_escrow_id are for, or what a successful open returns. It gestures at the workflow with 'then fund and query' but leaves the actual sibling tool names and sequence implicit, making it insufficient for confident invocation.

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 50%, so the tool description should compensate for undocumented params like max_queries, open_tx_hash, and proof_escrow_id. It does not explain these. The mention of '20 queries/session' and pricing is not clearly mapped to max_queries or any parameter, and the 'Listing: bleepingwatch' line reads like a specific example rather than general guidance for listing_id/listing_slug.

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 action: 'Buy per-query access to live data listings' and 'Open a prepaid session', identifying the resource as a data session. It also distinguishes itself from data_preview by explicitly pointing to the free first-taste path. However, it does not clearly differentiate itself from sibling tools like data_session_fund or data_session_query.

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 an explicit alternative for free access: 'first taste free via data_preview'. It also implies a follow-on workflow with 'then fund and query', but it does not name the actual sibling tools (data_session_fund, data_session_query, data_session_attach_escrow) or state when this tool should not be used. The usage guidance is present but only implicit.

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