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

Adds substantial behavior beyond the readOnly/openWorld annotations: nothing is marked read in the lemlist inbox, the 'Lead-Daten freigeben' workspace permission is required, limit caps at 100, per-message text is HTML-stripped and truncated to max_chars. These are exactly the side-effect, authorization and rate-limit facts an agent cannot infer 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?

Front-loaded with the action, then the returned fields, then the operational caveats (no read-marking, permission, limits). Dense but every clause adds an operational fact; nothing is filler.

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?

Given 4 parameters at 0% schema coverage and a permission-gated external API, the description covers input origins, caps, auth prerequisites and mutation side effects. The return-shape enumeration is partly redundant with the output schema, but it makes the tool callable without extra lookups.

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 0%, so the description carries the full burden and does: contact_id's origin, limit's ceiling of 100, max_chars as the truncation length, and workspace as an optional slug. All four parameters get meaning the schema does not provide.

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 and resource ('Nachrichtenverlauf mit einem Kontakt') and pins the scope by naming where contact_id comes from (lemlist_list_replies), which distinguishes it from the sibling that lists replies. An agent can tell what it retrieves without reading the 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 lemlist_list_replies as the prerequisite source for contact_id and explains the workspace parameter as optional only when a single workspace exists. It gives clear conditions for use but no explicit when-not-to-use exclusions beyond that.

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