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

Annotations already declare idempotentHint=true and destructiveHint=false, and 'Returns the existing cell if it is already open' largely restates that idempotency. The genuinely additive fact is the ordering constraint relative to memory writes, but there is no mention of permissions, cell lifecycle/closure, or error conditions.

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?

Two sentences, front-loaded with the action and scope, with no filler. The return-behavior note is placed last where it belongs.

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?

There is no output schema, and the description usefully states the return behavior for an already-open cell, which is the key return question. It omits auth/permission needs and the relationship to stage_commit, which would round it out for a mutation 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 all four parameters (brain, source, concept, entities) are already documented in the schema. The description only echoes the required 'source' and 'concept' pair and adds nothing about brain defaulting, entity shape, or limits.

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 concrete verb and resource ('Opens a build cell') and scopes it to exactly 'one source and one concept', with a gloss for the jargon term ('concept (topic)'). It does not name or differentiate against the obvious sibling stage_commit, which handles the staging lifecycle, so an agent must infer the relationship.

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 clear timing context: the cell is opened 'before its memories are written', which implies the correct position relative to memory_append/stage_commit. It also notes the already-open behavior. It stops short of explicit when-not-to-use guidance or naming alternatives.

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