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

Goes well beyond the readOnly/idempotent annotations by disclosing the auth requirement (SpaceNexus key on Professional or Research plan) and, importantly, the data-quality contract: amount is null when undisclosed or only approximate and is 'never estimated'. That is exactly the behavioral context an agent needs to avoid misreporting values.

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-loads the access prerequisite, then the resource and returned field inventory, then filtering/paging. Information-dense with no filler, though the second sentence is a long enumerated run-on that could be tightened.

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 carries the full return-value burden and does so thoroughly (date, amount and its null semantics, series/round type, valuation and basis, lead plus all listed investors, evidence type and source link). Auth, filtering and paging are all covered.

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% across all 8 parameters, so the schema already documents limit, since/until, stage, offset, company, investor and min_amount_usd. The description's 'filter by company, investor, stage, dates and amount; page with offset' restates those semantics and the lead-vs-listed-investor nuance without adding syntax or format detail.

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+resource with scope: 'the full published history of private funding rounds into space companies'. It explicitly contrasts its coverage with the last-90-days subset, which lets an agent distinguish it from the sibling recent_funding_rounds 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?

'Not only the last 90 days' plus the filter/paging sentence tells the agent when this tool is the right choice versus a recent-rounds tool. It does not name the alternative sibling by name or state exclusions, so it stops short of the top tier.

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