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

Annotations already declare readOnly/idempotent/non-destructive/false-openWorld, so the safety profile is covered. The description does add UI-level behavior beyond the annotations — a studio card is created, pressing it opens the chart held at the focus moment, with a way back — plus a semantic caveat ('a replay shows what printed, never a forecast') and the 10-minute-to-30-day window bound. That is real added context, but it omits things an agent may need, such as whether the card persists or replaces an existing one, or what happens if the studio is already showing something.

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?

Roughly 85 words for a six-parameter tool is proportionate, and the core action is front-loaded in the first clause. The prose is metaphor-heavy ('time compressor', 'held and ready to play') and packed into one unbroken block, costing a little density without wasting whole sentences.

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 safety annotations covering the read-only profile and no output schema to explain, the description carries what remains: what the tool does, where the result appears, eligibility bounds, and the no-forecast caveat. It is close to complete, missing only card lifecycle details and any mention of how the card is referenced later (e.g. by note or by window).

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 baseline is 3, but the description goes beyond it: it interprets 'focus' as the moment to hold on 'a trade, a sweep, a touch of a level' and ties 'speed' to the play-back rate, both of which give the enum and ISO fields practical meaning the schema alone does not. The note parameter is not mentioned in prose, and the from/to constraints are only implied by the ten-minute-to-thirty-day rule.

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?

'Put the trader's chart and its time compressor on a past window' names a specific verb and resource, and the card/chart-opens behavior makes the effect concrete. It is distinguishable from siblings like chart_state or image, but it never contrasts itself with near-neighbors such as replay_record or rehearse, so an agent must infer which replay-family tool to pick.

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 gives an explicit trigger: 'Use it whenever you talk about what happened in a window: show it on the chart instead of only describing it.' It also supplies hard eligibility bounds ('Past windows only, ten minutes to thirty days'). It stops short of naming an alternative when a user wants a static image or a rehearsed sequence instead.

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