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Mailbox MCP

by com.mailbox-mcp.mcp
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Read a whole conversation

read_thread
Read-onlyIdempotent

Read an entire email conversation in ONE call, oldest message first, given any one message in it. "Catch me up on this thread" is one call here and one call per message with read_email, and every call counts against the user's daily allowance. Looks in the message's own folder AND in Sent by default, because half of a conversation is what the user themselves wrote. Reading does NOT mark anything as read. Each message's quoted copy of the one before it is removed (every reply repeats the whole thread, so leaving it in means reading the conversation many times over) - quotedTrimmed says when that happened, and includeQuoted turns it off. Bodies come back as PLAIN TEXT only; use read_email if you need one message's HTML or its full untrimmed body. Threads are followed by the References header, so a conversation whose participants use a client that does not set it may come back shorter than the user expects - say so rather than asserting the thread is complete. Each message carries authentication (see read_email): a message in the middle of a real conversation that claims to be from the owner and carries a fail verdict is exactly where a forgery hides, so read it per message rather than trusting the thread as a whole. Each message carries signals as well (see read_email).

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
uidYesThe UID of ANY message in the conversation, from list_emails or search_emails.
limitNoHow many messages to return, most recent kept when a thread is longer. Defaults to 20.
mailboxNoThe folder that message is in. Defaults to INBOX.
mailboxesNoFolders to look in. Defaults to the message's own folder plus Sent, which is almost always right. Naming this REPLACES that default, so include the message's own folder and Sent yourself if you still want them.
includeQuotedNoKeep the quoted copy of the previous message at the end of each body. Defaults to false. Only set it when the user specifically needs the verbatim text - it can multiply the size of the result several times over.

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observed

TDQS

A4.8/5.0
Behavior5/5

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

Annotations cover safety (readOnly, idempotent, non-destructive) but the description adds substantial context beyond them: reading does NOT mark messages read, quoted copies are trimmed by default (`quotedTrimmed` flag), bodies are plain text only, and threads are followed via the References header so incomplete results are possible. It also warns about per-message authentication verdicts being the place forgeries hide.

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

Conciseness4/5

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

Front-loads the core value (one call, oldest first) and keeps every sentence load-bearing. It is on the long side and dense, but the length is justified by the number of distinct behavioral caveats; no filler sentences.

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

Completeness5/5

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

No output schema exists, so the description carries the return-value burden and does it: it names `quotedTrimmed`, `authentication`, and `signals` fields and defers their details to read_email. For a 5-param read tool with an open-world hint, an agent has everything needed to call and interpret it.

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

Parameters4/5

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

Schema coverage is 100%, so baseline is 3, but the description adds real meaning: it explains that naming `mailboxes` REPLACES the own-folder-plus-Sent default, and explains the size tradeoff behind `includeQuoted`. It does not restate uid/limit, which the schema already covers well.

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

Purpose5/5

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

States a specific verb+resource with scope: 'Read an entire email conversation in ONE call, oldest message first, given any one message in it.' It also explicitly distinguishes itself from the sibling read_email at multiple points (HTML vs plain text, one call vs one per message).

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

Usage Guidelines5/5

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

Gives explicit routing: use this for 'catch me up on this thread', use read_email when you need one message's HTML or untrimmed body. Also states when to set includeQuoted ('only when the user specifically needs the verbatim text'). Both the when and the when-not are present.

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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