Drafts an invoice email in Mail.app with the invoice PDF attached, so you can review and send it yourself.
Otevře v Mail.app KONCEPT e-mailu s PDF fakturou v příloze. Nic neodesílá — odeslání je na uživateli.
| Name | Required | Description | Default |
|---|---|---|---|
| to | No | Adresát. Default e-mail odběratele z adresáře. | |
| number | Yes | Číslo faktury z evidence. | |
| message | No | Vlastní text e-mailu místo výchozího. |
| Name | Required | Description | Default |
|---|---|---|---|
| result | Yes |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden and does disclose the two behaviors that matter most: it writes into a local Mail.app mailbox (side effect on the user's machine) and it never transmits anything. Gaps remain around preconditions — the invoice presumably must exist and be issued, and Mail.app must be present on macOS — and around failure behavior for an unknown number.
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?
Two short sentences, front-loaded with the action and followed immediately by the non-sending guarantee. No filler, no restatement of the name.
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 no explanation, and the parameter set is small and fully described. What is missing for a tool that touches the user's mail client is precondition and failure context (invoice must exist, Mail.app required), which keeps it short of a 5.
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 100%, so the field meanings (recipient defaulting to the customer's address from the directory, invoice number, custom message body) are already fully documented in the schema. The description adds nothing parameter-specific beyond implying that a PDF for that invoice gets attached.
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 states a concrete verb and artifact: it opens a DRAFT email in Mail.app with the invoice PDF attached. The added 'Nic neodesílá' immediately separates it from the sending/issuing siblings such as issue_invoice, so an agent can place it without opening 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 makes the key usage boundary explicit — this prepares a draft, sending is left to the user — which is exactly the distinction an agent needs before choosing a mail-related action. It does not, however, say what to do if the invoice is not yet issued (issue_invoice first) or which sibling to prefer for other mail tasks.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.