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

Annotations already declare readOnlyHint=false and destructiveHint=true, so the safety profile is conveyed structurally. The description adds the auth requirement ('Needs the write scope') and the .md-only constraint, but does not explain what the destructive behavior actually means (overwrite? append? irreversibility), which is the key gap for a destructive write.

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 tight sentence with the core constraint front-loaded; nothing is wasted. It is arguably too terse for a destructive write, but as pure structure it is efficient.

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 annotations and an output schema present, the description needn't explain returns or safety, and it does cover auth and file-type constraints. However, for a destructiveHint=true write it omits whether an existing file is overwritten, which is material context an agent needs before calling it.

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% for both params, so the baseline is 3. The description's '.md paths only' merely restates the schema's own 'must end in .md' constraint and adds no syntax, format, or content-size detail beyond the structured data.

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 ('Write one Brand Memory file') and its purpose ('the agent grounds future posts in it'), which cleanly separates it from read-oriented siblings like brain_read and brain_tree. It doesn't explicitly name the alternates, so it stops short of a 5.

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 gives a precondition ('Needs the write scope') and hints at downstream use ('grounds future posts'), but offers no explicit when-to-use vs. when-not guidance, no mention of overwrite semantics versus siblings, and no exclusion conditions.

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