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

Beyond the annotations (readOnlyHint=false, destructiveHint=false, openWorldHint=false), the description discloses real behavior: the write is immediate, a Personal Space is auto-created when absent, idempotency_key should be reused on retry after a timeout, and text/sources are untrusted data that do not grant permission. That last point is a meaningful security disclosure for an ingestion path. Not a 5 because it says nothing about versioning/provenance effects or what a duplicate idempotency_key does to an existing entry.

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 short sentences with the action, destination default, and trust caveat front-loaded; there is no filler. Density is high but each sentence carries distinct information, so nothing feels wasteful.

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?

The output schema exists, so return values need no explanation, and the safety profile is covered by annotations. Still, for an 8-parameter create tool with nested objects and a provenance graph, the definition leaves the kind taxonomy and provenance semantics entirely undocumented, which is a substantive gap for correct invocation.

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 only 25%, so the description must carry more weight. It does add real meaning for space_id (defaulting and auto-creation) and reinforces idempotency_key retry semantics, and it frames text/sources as untrusted reference data. But the six-value kind enum, provenance, and the nested premise_knowledge_ids/premise_versions fields get no explanation at all, and those are the parameters most likely to be misused.

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?

The description gives a specific verb + resource ('Save a new entry in a private Space') plus immediacy and idempotency, so an agent knows this is a write-to-knowledge-base operation. It does not explicitly name the sibling it replaces (knowledge_propose, knowledge_update, skill_create), so differentiation is left partly to inference.

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?

It states the default destination ('Writes to your Personal Space unless space_id names another, creating Personal when needed'), which is genuine routing guidance for the space_id choice. However it never says when to use this instead of knowledge_propose (for staged/suggested entries) or knowledge_update (for changes to existing entries), which are the obvious alternatives in the sibling list.

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