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

Goes well beyond the single readOnlyHint=false annotation: dry-run default, idempotency/replay semantics ({replay: true}), the fact that a rejection is a normal non-error response that must be read and relayed, credential requirements, the 20-fills-per-UTC-day cap, and the practice-money disclaimer in _meta. This is exactly the behavioral context an agent needs before a mutation.

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?

Dense single paragraph, but front-loaded with the most decision-relevant facts (WRITE opt-in, dry-run default, sibling mutating tool). Some clauses repeat schema-level constraints (shares 1..1,000,000, thesis 250 chars), which slightly dilutes the signal without making it hard to parse.

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?

No output schema exists, and the description compensates by sketching the return shapes for both dry-run and replay responses, plus error semantics, auth, and rate limits. For a 6-parameter mutating tool with only one annotation, nothing an agent needs to invoke it safely 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 description coverage is 100%, so the baseline is 3; the description still adds meaning by tying _dry_run and _idempotency_key together as a two-step execute protocol and framing thesis as the USER's own reason rather than the agent's. It largely restates the shares/side bounds already in the schema, so it does not fully escape redundancy.

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?

Opens with a specific verb+resource+scope: 'place a market order in YOUR paper (practice) portfolio', and immediately contrasts the paper engine with real money/accounts. It also positions itself among siblings by naming the only other mutating tool (reading_list_annotate), so an agent can distinguish it from the many read-only ol_* tools.

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 operational context: dry-run is the default, execution requires re-calling with _dry_run: false plus the same _idempotency_key, and auth must be an API key or OAuth token (cookies refused). It does not state explicit exclusions (e.g., when to prefer ol_paper_portfolio instead), but the workflow conditions are unambiguous.

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