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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuine behavioral nuance beyond them: the funding figure for a listed company represents pre-listing private rounds, and fundingBasis signals which rule applies, plus Space Score is only present when ranked. It does not, however, state anything about match fuzziness or empty results.

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?

A single dense sentence, but it is front-loaded with the core payload (profile facts) and each clause corresponds to an actual returned field. It avoids filler, though the fundingBasis parenthetical makes it slightly heavy to parse at a glance.

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 properly compensates by enumerating the returned fields and qualifying two edge cases (pre-listing funding rule, conditional Space Score). Combined with annotations covering safety, an agent has enough to call it correctly; only the sibling-routing gap keeps it from a 5.

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%, and the query parameter already documents accepted forms (name, slug, ticker) with examples, so the schema carries the parameter burden. The description adds nothing about the limit parameter or match semantics, making the baseline 3 appropriate.

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 (lookup) plus resource (space company) and enumerates the profile fields returned, so an agent knows exactly what comes back. However, it does not differentiate itself from siblings that also return company-adjacent data (funding_round_history, recent_funding_rounds, space_score_history), leaving overlap ambiguity.

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?

Usage is only implied: the field list suggests this is the profile-facts tool rather than a history tool, but there is no explicit when-to-use, no exclusions, and no named alternative for funding or score history lookups. An agent must infer the boundary against three similar siblings.

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