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

Goes well beyond the annotations: it spells out the operational consequence (no messages, manual or automated, until removed), confirms reversibility and that nothing is erased or cancelled, and discloses the implementation (system tag 'Blacklist' + organisation registry), which matters for anyone reading state elsewhere.

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?

Purpose leads, then scope requirement, then effect, then reversibility mechanics — a sensible order with no filler. The final clause about not being a parallel shortcut is slightly defensive but still informative.

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?

Covers prerequisites, side effects, reversibility and internal mechanism for a state-changing tool, backed by annotations and a fully documented schema. The only gap is that with no output schema the description never hints at what a successful call returns.

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 already 100%, so the baseline is 3; the description still adds behavioral meaning to `blacklisted` (false removes the block, fully reversible) and to the preservation of `reason`, which the schema only states mechanically.

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 precise verb pair and resource ('Pose ou retire la liste noire sur un contact'), which makes the write/toggle nature unambiguous versus the read-only ficiel_get_blacklist. It never names that sibling explicitly, so the differentiation is inferable rather than stated.

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 a real prerequisite ('Portée « write » requise') and the condition under which the tool matters (a contact must stop receiving manual and automatic messages). It stops short of explicit when-to-use/when-not guidance or pointing at ficiel_get_blacklist to inspect current state first.

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