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lob

by io.usefulapi

Send a postcard (COSTS MONEY)

lob_create_postcard
Destructive

⚠️ SENDS A REAL POSTCARD and charges your Lob account (use a test_ key to avoid real mail/charges). to and from accept an existing address id (adr_…) or an inline address object. front/back accept an HTML string, a hosted asset URL, or a template id (tmpl_…). Cancelable only before send_date. Lob API: POST /v1/postcards.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
toYesEither an existing address id (adr_…) or an inline address object.
backYesBack artwork: HTML string, asset URL, or template id (tmpl_…).
fromNoReturn address (id or inline object). Optional.
sizeNoPostcard size. Default 4x6.
frontYesFront artwork: HTML string, asset URL, or template id (tmpl_…).
mail_typeNoUSPS mail class.
send_dateNoISO-8601 date/time to schedule the send (future). Cancelable until then.
descriptionNoInternal label.
merge_variablesNoKey/value data merged into HTML templates.

TDQS

A3.7/5.0
Behavior5/5

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

The description adds significant behavioral context beyond the destructiveHint annotation: it warns about real costs, suggests using test keys for safety, explains cancellation only before send_date, and details parameter type flexibility (id vs inline, HTML vs URL vs template).

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is compact and front-loaded with the critical warning. Every sentence adds value, covering key behavioral notes, parameter flexibility, and cancellation policy without redundancy.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the complexity (9 params, no output schema), the description covers main behaviors and key parameters but omits details on the return value (e.g., created postcard object), size/mail_type options, and merge_variables. Schema fills some gaps but output information is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3. The description reinforces parameter types (address id vs inline, artwork formats) and adds send_date cancelability note, but mostly restates schema info without much new meaning.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool 'SENDS A REAL POSTCARD and charges your Lob account', making the action and resource explicit. However, it does not differentiate from similar sibling tools like lob_create_letter, lacking explicit sibling distinction for a top score.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides no guidance on when to use this tool over alternatives such as lob_create_letter or lob_cancel_postcard. It only offers a caution about using test keys, not usage context.

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

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TDQS

A3.9/5.0
Disambiguation5/5

Every tool targets a distinct resource and action, with clear verb-noun names like create_address and verify_us_address. There is no overlapping functionality, and even similar operations (e.g., list for different resources) are distinct.

Naming Consistency5/5

All tools share the 'lob_' prefix and follow a consistent verb_noun pattern (e.g., create_postcard, list_letters, verify_intl_address). Multi-word nouns use underscores, maintaining uniformity throughout.

Tool Count5/5

With 18 tools, the set covers the primary mail fulfillment operations—address management, postcards, letters, checks, self-mailers, and address verification—without feeling bloated or sparse. The count is well-suited to the domain.

Completeness2/5

The tool set has notable gaps: no create_check or create_self_mailer, no cancel for letters or checks despite being referenced, no update/delete for addresses, and only list for templates. These missing operations will likely cause agent failures in common workflows.

Resources