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

Beyond the readOnly/destructive annotations, the description adds a meaningful side-effect boundary: files are only ever written inside the configured download directory and the mailbox is not modified. It also discloses that the saved path is returned, though it does not cover overwrite or failure behavior.

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?

Three short sentences lead with the action, state the return value, and then give a safety constraint. No filler or repetition of schema content.

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 single-file download with only three parameters, an output schema, and safety annotations, the description plus schema is complete. It covers the destination, return value, and non-mutation guarantee.

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 parameter meaning is fully carried by the schema. The description adds no separate parameter detail, which matches the baseline: the schema does the heavy lifting.

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 opens with a specific verb and resource: 'Download one attachment into the configured download directory.' This clearly distinguishes it from sibling listing/reading tools and states the output (saved path).

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?

The operation is clear enough that an agent knows to call it when an attachment from a message is needed, and the schema ties `part_id` to `read_message`, giving context. However, the description itself names no alternative or explicit when-not-to-use condition, so it stops just short of full routing guidance.

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

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

Annotations already establish that this is a read-only, non-destructive operation. The description adds value by disclosing that the tool reports authentication state and is intended as an initial diagnostic step, but it does not go further into behavioral details. No contradiction exists.

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?

The description is two concise sentences with no filler. The first sentence states the core function, and the second provides actionable guidance, placing the most important information upfront.

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 zero parameters, read-only annotations, and an output schema, the description fully covers what an agent needs: what the tool does, what information it returns, and when to use it. Nothing essential is missing.

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?

The tool has zero parameters, so the description does not need to document input semantics. A baseline of 4 is appropriate, and the description introduces no conflicting or missing input information.

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 uses a specific verb ('List'), a clear resource ('configured mail accounts'), and states the key attribute returned ('whether each is authenticated'). This clearly distinguishes it from sibling tools that operate on folders, messages, or attachments.

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?

The description gives explicit guidance: call this tool first if another tool reports an authentication problem. It does not state exclusions or alternative tools, but the diagnostic use case is clearly framed and sufficient for a zero-parameter tool.

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

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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the read-only nature is covered. The description adds useful behavioral context: output includes message/unread counts and normalized role values that are stable across providers, which is meaningful beyond the 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?

The description is compact and front-loaded with the core purpose. The second sentence adds valuable cross-provider context, though its phrasing about asking for 'junk' could be slightly clearer in relation to this specific tool.

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 simple read-only tool with one optional parameter and an output schema, the description covers the core behavior and adds useful output context. It is complete enough for an agent to invoke correctly, though a brief usage scenario would make it stronger.

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% and the only parameter, account, is already described in the schema. The description does not add parameter-level detail beyond what the schema provides, so the baseline score of 3 applies.

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: 'List the folders in a mailbox' with the additional detail of message and unread counts. This clearly differentiates it from sibling tools like list_messages and list_accounts.

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?

No explicit guidance on when to use this tool versus siblings such as list_messages or search_messages. The note about normalized roles hints at cross-provider usability but does not explain when an agent should invoke list_folders instead of another tool.

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

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

Annotations already mark this as read-only, but the description adds meaningful behavioral detail: it returns summaries only, includes a handle for retrieving full messages, and orders results newest first. This goes beyond what annotations or schema provide and helps an agent predict the tool's behavior accurately.

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?

The description is two short paragraphs with zero filler. The primary purpose is front-loaded in the first sentence, and the second paragraph adds the essential return-handling detail. Every sentence earns its place.

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 list-type tool with no required parameters, an output schema, and annotations covering the safety profile, the description is complete. It covers ordering, summary-only behavior, the handle handoff to read_message, and the folder-scoped browsing model. Nothing an agent needs to decide whether to call it or how to use its output is missing.

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%, with all five parameters already clearly documented (limit, folder, offset, account, unread_only). The description adds no parameter-specific information, which is acceptable because the schema carries the full burden. Baseline 3 is appropriate here.

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 clearly states the tool's action ('Browse messages in a folder'), the sorting order ('newest first'), and the response scope ('summaries only (no bodies)'). It also distinguishes itself from read_message by explicitly directing the agent to use read_message for full text, which differentiates it from a key sibling.

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?

The description gives clear context for when to use this tool (browsing folder summaries) and explicitly routes the agent to read_message for full bodies. It does not explicitly contrast with search_messages, but the browsing vs. searching distinction is implied by the description and sibling names, so the guidance is adequate but not exhaustive.

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

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

Beyond the readOnlyHint and destructiveHint annotations, the description adds meaningful behavioral details: HTML-only mail is converted to text, and reading does not mark the message as read. This helps the agent predict side effects and format transformations.

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?

The description is two short, focused sentences with no filler. The core action is stated first, and behavioral caveats follow immediately, making it easy to scan and act on.

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 read-only message-retrieval tool with fully documented parameters, a rich output schema, and safety annotations, the description covers the essential behavior and side effects. Nothing critical is missing for an agent to invoke 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 description coverage is 100%, so the schema already documents all three parameters. The description adds context about full-message content and truncation behavior but does not materially extend the parameter semantics 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?

The description uses a specific verb and resource: 'Read one message in full' with explicit content types (headers, body text, attachment metadata). This clearly distinguishes it from listing or searching messages and from fetching attachment content directly.

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?

The description clearly implies use when full message content is needed, and the handle parameter references list_messages/search_messages, grounding the workflow. It does not explicitly contrast with get_attachment for actual attachment bytes, but the scope is clear enough.

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

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

Annotations already mark it read-only and non-destructive. The description adds useful behavioral details beyond that: it is a server-side IMAP search, scans the whole folder without downloading, and returns newest-first results. This is meaningful context, though it doesn't cover edge cases like empty criteria or pagination behavior.

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?

Three short sentences, front-loaded with the purpose, then combination semantics, then operational behavior. No filler and each sentence contributes unique information.

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 the output schema exists and the input schema is fully documented, the description covers the essential context: folder scope, criteria conjunction, server-side execution, and ordering. It is complete enough for confident invocation, though mentioning list_messages as a no-filter alternative would have made it slightly more complete.

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?

All 10 parameters already have schema descriptions, so the baseline is 3. The description adds the key interaction rule that all supplied criteria are combined with AND, which is not captured in the schema. It doesn't need to repeat individual parameter meanings.

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 names a specific operation ('Search a folder') and clarifies the filtering semantics ('All supplied criteria are combined with AND'). It is clear what the tool does, but it doesn't explicitly contrast it with sibling list_messages, so it falls just short of full differentiation.

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?

The description establishes a clear use case: searching a folder rather than simply listing it. It doesn't explicitly say when not to use it or name an alternative, but the server-side, criteria-based behavior gives an agent clear context for selecting it.

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