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

Annotations only declare readOnlyHint=false, so the description carries the burden and delivers richly: dry-run default, idempotency/ replay semantics ('without placing twice'), rejection being a normal non-error response, API-key/OAuth requirement (browser cookie refused), and a 20-fills-per-UTC-day cap. These are exactly the beyond-annotation traits an agent needs.

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-loaded with 'WRITE (opt-in)' and organized around the operational flow. It is dense and long, but for a stateful two-step mutating tool nearly every sentence earns its place; only the restated share/side ranges are mildly 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?

Despite no output schema, the description discloses the response shapes ({dry_run...}, {replay: true...}), auth needs, rate limits, and the practice-money disclaimer location (_meta.disclaimer). Nothing an agent needs to call and safely relay results is missing.

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% (baseline 3), but the description adds real meaning about the interaction between parameters: that the _idempotency_key returned by the dry run must be reused to execute, and framing thesis as the USER's own reason rather than the agent's. It largely restates the ranges (shares 1..1,000,000) already in the schema, so it stops short of a 5.

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 ('place a market order') and resource ('YOUR paper (practice) portfolio') with scope, and explicitly distinguishes itself from siblings by noting it is 'One of TWO mutating tools here (the other is reading_list_annotate).' An agent can identify it without opening any 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 explicit when-to-use (placing paper trades), the default-and-recall procedure for the dry run, the exact condition to execute (_dry_run: false plus the same _idempotency_key), and names the alternative mutating tool. Nothing is left to inference.

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