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

Annotations cover the safety profile (readOnly=true, destructive=false, openWorld=true), so the description's job is to add context — and it does, disclosing the subscription/trial model, per-call x402 payment path, and the exact no-access behavior. It still does not explain the idempotentHint=false beside a readOnly read (i.e. that repeated calls return different live data), which would have closed the loop.

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?

Front-loaded with what the tool returns before the access caveats, and every sentence carries information. The middle payment/subscription sentences are slightly dense but all necessary for correct invocation.

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?

There is no output schema, so the description must carry return-shape burden — and it names the returned fields (coil_score / coil_kind / coil_note) as well as the PaymentRequired failure object. For a single-parameter live read, nothing an agent needs to invoke it correctly is missing.

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?

Only one parameter, and schema coverage is 100% with the ticker example 'NVDA' already in the schema. The description's 'One stock's ...' reinforces single-symbol scope but adds no format, case, or exchange-qualifier detail beyond the schema. Baseline 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?

States a specific verb+resource ('One stock's current-session scores and entry state') and adds the distinctive payload (coil_score / coil_kind / coil_note). The phrase 'Live intraday version' explicitly separates it from the sibling get_stock_read, so an agent can choose between the two without opening a 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?

Gives concrete access conditions: Coil Live subscribers connect the connector and sign in, or an agent with an x402 wallet pays per call. It also states the failure mode when neither applies (PaymentRequired, no data), which implicitly routes the agent to the non-live sibling. It stops short of naming get_stock_read as the explicit fallback for unsubscribed callers.

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