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

With no annotations, the description carries the full burden and does well: it discloses the single-live-entry constraint, destructive overwrite on re-write, the explicit-purge lifecycle, and the scope resolution order (header X-Project-Scope, then SCOPE_DEFAULT, with 'global' forcing NULL scope, read only under Pro). It does not cover permissions for writing or error/idempotency behavior, so it is not fully complete.

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?

The core mutation and overwrite rule are front-loaded in the first two sentences, and the scope guidance is grouped logically. There is mild redundancy: the purge/activate lifecycle is restated in the closing line about the next activation serving the content 'in its place.'

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?

An output schema exists, so return values need not be described, and the description still adds the non-obvious fact that the stored content surfaces at the next activate rather than being returned by the write. Combined with scope resolution and content limits, this covers what an agent needs, though write permissions and failure behavior are unaddressed.

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 coverage is 0%, so the description must compensate, and it does for two of three parameters: project_scope gets detailed resolution semantics (omitted → session scope; 'global' → NULL scope) and content_md gets a 6 000 character cap plus guidance to record facts, code, paths and figures verbatim. persona_slug is only implied by the '(persona, scope)' pairing and never explained.

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 opens with a precise verb+resource: upserting the ephemeral previous-context keyed by (persona, scope). It states the uniqueness rule ('Une seule entrée live par (human, persona, scope)') and the overwrite semantics, which separates it cleanly from clear_previous_context and the update_semantic/update_procedural siblings.

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 explains the lifecycle: content is served on the next activate(persona_slug, project_scope) and must then be purged explicitly via clear_previous_context, which tells the agent where this fits in the workflow. It also gives a rule for choosing 'global' vs. project scope. It stops short of stating when an agent should prefer this over write_event or update_semantic.

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