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

Beyond the readOnly/openWorld annotations, the description discloses the data provenance (SEC filings), the fixed as-of date, the sort order, a hard result cap on the free tier, and the exact paid-access mechanics ($0.25 per call over x402 in USDC on Base, or a Tensorust key). That is precisely the billing and coverage context an agent needs before calling and is not derivable from the structured fields.

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, front-loaded with the definition of the dataset before the access/pricing terms. Every clause carries information (criteria, date, ordering, free cap, paid fields, price), though the second sentence is dense enough that a reader must parse payment mechanics and return fields in one pass.

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 single-boolean, read-only query tool with no output schema and fully covered params, this covers selection criteria, ordering, result contents, caps and cost. The only gaps are the snapshot's fixed date (no date parameter exists, which could surprise an agent wanting another quarter) and any indication of list size beyond the top-10 cap.

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% and the single parameter already carries a description, so the baseline is 3. The tool description still adds genuine meaning: it enumerates what the paid response contains (every fund's mark, par, prior-quarter mark, filing link) and clarifies that the default non-full behavior is the free top-10 view, which the schema alone does not convey.

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 precise verb-and-resource outcome: US first-lien loans where two or more BDC managers mark 10+ points apart at a specific as-of date, drawn from SEC filings, ordered widest-gap-first, returning borrower, low/high manager, marks and par. This is specific enough to separate it from the sibling lender_marks without opening either 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?

Clear usage context is given via the tiering rule: the default call is free and returns only the top 10, while full=true returns the complete list. What is missing is an explicit statement of when to prefer this over a sibling such as lender_marks (e.g., single-manager marks vs. cross-manager dispersion) or any exclusion condition.

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