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

Annotations already declare readOnly/openWorld/non-destructive, and the description adds real behavioral value beyond them: venue fetch when candles[] is omitted, cached past sessions for speed, network-free reproducibility when candles are supplied, and an error when a session has no candles. It also states the output is descriptive and not a trading signal, which is important framing.

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 core purpose is front-loaded, but the tail is a cluttered edge-case dump that repeats itself: "session_date must be a completed UTC session, before today" and "a session with no candles returns an error" each appear twice, and the venue/instrument constraints are restated. Several sentences could be merged without losing information.

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?

With no output schema, the description compensates by enumerating return fields (state, accepted, direction, confidence, key_levels VAH/VAL/VPOC, scenario_framing, invalidation) and covering input validity, caching, and offline reproducibility. An agent has everything needed to invoke it correctly and interpret the result.

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 coverage is 100%, so the schema already documents every parameter including enums and defaults. The description reinforces key constraints (default 15m timeframe, value_area_rule 0.5–0.9, include_delta default true), but adds little parameter meaning beyond that and never mentions the optional prev_candles input.

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 analytical question — whether price accepted (held) beyond the value area or rejected back inside as a fakeout — and defines the two outcomes (accepted / reject). It is clearly more specific than the name alone, though it never names a sibling (e.g. run_session_structure) to sharpen the boundary.

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 concrete usage prompt ("did the break above VAH get accepted?") and a "Not covered" block excluding order flow beyond supplied candles, other venues, and forward-looking predictions. It does not route the agent toward or away from any named alternative tool, so it stops short of a 5.

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