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

Goes well beyond annotations: acts on behalf of and under the account holder's name, no private inbox/no foreign identity, first message creates a chat while later ones continue it, max 20/hour, and mandatory user confirmation before sending. No contradiction with annotations.

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?

Every sentence adds operational value: action, intended use, identity framing, parameter sourcing, chat lifecycle, content guidance, rate limit, and confirmation requirement. It is front-loaded with the core action and stays focused.

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 two-parameter send action with no output schema, the description covers prerequisites, behavioral effects, limits, and user-confirmation needs. There are no significant gaps that would prevent an agent from invoking it correctly.

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 already documents both parameters at 100% coverage. The description adds value by telling the agent the post_id must come from markt_ansehen or meine_treffer and instructs content quality ('Schreib konkret und sag dazu, worum es geht'), which is beyond the schema.

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 action: 'Schreibt der Person hinter einem Eintrag ueber den Marktplatz-Chat von Open Platform.' This clearly identifies the verb, resource, and channel, and the sentence 'Das ist die dafuer vorgesehene Kontaktaufnahme' plus the distinction from private inbox/foreign identity differentiates it from read or management 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?

Provides clear when-to-use context: contacting someone who publicly posted a listing and expects to be contacted. It also tells the agent where to obtain post_id from markt_ansehen or meine_treffer and to show the text before sending, but it does not explicitly name alternative tools or state when not to use it.

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