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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety is covered; the description adds genuinely new behavior — result ordering ("the calls that changed last night first") and the fact that the call is the same one every reader sees, i.e. not personalized. It also carries an output-presentation obligation ("Show the not-advice line and the run date") that an agent would otherwise miss. It stops short of 5 only because it says nothing about staleness, caching, or what happens when a watchlist is empty.

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?

Two sentences, both earning their place: the first defines the payload and its ordering, the second states a mandatory presentation rule. The payload definition is front-loaded and there is no filler or restatement of the title.

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?

An output schema exists, so the description need not spell out return values, yet it still sketches the shape (lists → stocks → published call) and pins the ordering. What is missing is minor: no note on empty watchlists, the not-advice line's source, or how "run date" relates to the data's freshness.

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?

The tool takes zero parameters, so the baseline is 4; there is no parameter semantics for the description to compensate for. Nothing in the description misdescribes the empty input schema.

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 names a concrete resource ("the signed-in person's StockMap watchlists") and specifies what is returned for each list: its stocks plus the model's published call on each. That implicitly separates it from the single-stock sibling stock_call and from the mutating watch/unwatch pair, but it never names an alternative outright, so it falls short of full sibling differentiation.

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?

Usage is only implied: an agent can infer this is the read path for a personal watchlist, and that watch/unwatch are the write paths. There is no explicit "use this when..." or "do not use for..." statement, and no mention of prerequisites such as being signed in beyond the passing phrase "signed-in person's".

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