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

Beyond the annotations (which already flag non-readonly, non-destructive, idempotent), the description explains the concrete idempotent behavior ('adding a starred symbol or removing an absent one is a no-op') and adds the auth scope requirement and the reassurance 'it never trades'. These are genuine behavioral additions beyond the hints.

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?

Three dense sentences, front-loaded with purpose, then idempotency, then symbol formats and a side-effect boundary. Every clause carries information and nothing is padded.

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?

For a 2-parameter mutation with no output schema, the description covers purpose, both parameters, auth scope, idempotency semantics, and the assurance that no trading occurs. An agent has everything needed to invoke it correctly.

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?

With only 50% schema description coverage (action is an undescribed enum), the description carries much of the load: it maps action=add/remove to outcomes and defines the canonical symbol taxonomy (perp ticker, spot pair, HIP-3 'xyz:TSLA', spot index '@107'). The '@107' format is not present in the schema, so this is real added meaning, though action values are just restated from the enum.

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 ('Add a symbol to YOUR watchlist ... or remove it') plus the exact action values that select each direction. An agent can immediately distinguish this mutation tool from the read sibling get_watchlist without opening the 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 clear in-tool routing via action=add/remove and states the required scope ('requires api:account'), so the agent knows the precondition. It stops short of naming an explicit alternative (e.g. get_watchlist to read, or when-not-to-use), so it is strong but not fully prescriptive.

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