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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds genuine value annotations cannot: the entitlement-gated API key requirement and the content of each reading, including that reasons are limited to 'where the stored inputs can say'.

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 sentences with little waste, and the prerequisite is front-loaded before the payload description. The final sentence on company_lookup is a useful routing cue rather than filler, though the first sentence is slightly dense.

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 enumerates what a reading contains and bounds the window to 365 days. Combined with the auth caveat and the sibling cross-reference, an agent has everything needed to call it correctly.

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 both parameters are documented in the schema. The description only echoes 'up to 365 days', adding no syntax or format detail beyond the schema; baseline 3 applies.

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 resource (daily Space Score readings for one company, up to 365 days) and enumerates the returned fields: score, rank, change, flagged large moves, and reason. It also distinguishes itself from the sibling company_lookup, which only serves the current score.

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?

Explicitly routes the agent to company_lookup when only the current score is needed and states the prerequisite (a SpaceNexus API key whose owner has the Research product). Clear context, though it doesn't spell out failure behavior when the key lacks the entitlement.

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