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

Annotations already declare readOnlyHint=true and destructiveHint=false, yet the description still adds real context: API-key requirement, the free-plan behavior where entry/stop-loss/take-profit/leverage come back null, and the not-found error path. It stops short of noting rate limits or pagination, but for a single-record read those are largely irrelevant.

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-loads the core action, then routes the agent to siblings, then states auth and plan caveats, then return shapes. Every sentence carries a distinct load and nothing is redundant with the schema.

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's explicit return contract ({ success, signal, plan } and the not-found error) is necessary and present. With annotations covering the safety profile and the schema covering params, an agent has everything needed to call and interpret this tool.

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 both parameters (apiKey, signalId) are already documented in the schema, including the signup URL. The description adds little parameter-level detail beyond restating the ID lookup, so the 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 and resource ('Get one signal by its ID') and immediately scopes it to 'live or already resolved', which distinguishes it from get_signals (list) and get_signal_history. The enumerated contents (reasoning, live price, PnL, verification outcome) tell an agent exactly what a call yields.

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?

Explicitly names the trigger ('use it to follow up a signal from get_signals or get_signal_history') and the second scenario ('see how a past signal ended'). The alternatives are named rather than left to inference, so selection between the three sibling read tools is unambiguous.

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