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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds real context beyond that: deterministic ordering ('newest first'), the kinds of events included, and that each row carries its repriced company and its own currency — useful for interpreting output without opening a schema (there is none).

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 tight sentences with the scope and ordering front-loaded, followed by the optional filter and the output currency caveat. No filler, and every sentence carries information an agent can act on.

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?

With no output schema, the description steps in to describe the row shape (company per mark, currency per row), which is the critical missing piece. Pagination behavior is left to the schema, which documents page/per_page adequately, so the definition is nearly complete for a 3-param list tool.

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 page, per_page, and company are already documented in the schema — baseline is 3. The description restates the company-scoping behavior and adds a currency-per-row detail, but that is a return-value concern rather than parameter semantics, so it does not materially exceed the 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?

States a specific verb and resource ('List valuation marks across the authenticated user's portfolio') and enumerates the mark types covered — funding rounds, secondaries, estimates, dissolutions. This clearly distinguishes it from siblings like list_metrics, list_transactions, and get_portfolio_history.

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 a concrete usage condition: 'Pass a company slug to scope to one company,' which tells the agent how to narrow results. However, it does not name an alternative tool or state when to prefer list_transactions or get_portfolio_history over this one, so the routing guidance is implicit rather than explicit.

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