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

Annotations already declare readOnlyHint=false, idempotentHint=true, and destructiveHint=false, so the safety profile is partially covered. The description adds valuable context beyond that: the scope of the write ('changes memory, never anything public'), the reversibility condition ('a fact struck out without a reason cannot be restored'), and the cost ('Free'). It does not reinforce the idempotent behaviour the annotation claims, which keeps it short of a 5.

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 primary action and its consequence front-loaded, followed by input requirements, then side-effect scope. Nothing is redundant with the annotations, and even the terse 'Free.' carries cost information.

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?

For a simple, three-parameter mutation with no output schema, the description covers the action, the consequence, the mandatory input, the blast radius, and the cost. The one missing piece is what happens when replacement_fact_id is supplied — whether recall then points to the replacement — which is a meaningful behavioural detail for this 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 coverage is 100% and both required parameters already carry descriptions ('Why it is no longer true. Required.' and 'The id of the fact, from recall.'), so the schema does most of the work and the baseline is 3. The description only reinforces the required reason and its consequence, and never mentions the optional replacement_fact_id, so it adds little beyond the structured fields.

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 ('Mark a remembered fact as finished') plus the concrete effect ('so it is never proposed again'), and explicitly separates itself from the sibling set with 'the only one of these tools that changes anything.' An agent can identify the resource, the outcome, and its uniqueness among siblings without opening any schema.

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 routes the agent to a sibling for the input ('the fact id from recall') and states a hard precondition (a reason is mandatory). It also tells the agent this is the mutating path versus the read-only siblings. The only gap is the absence of an explicit when-not-to-use condition, such as not superseding a fact that is still true.

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