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

With destructiveHint=true in annotations, the description adds valuable context by specifying the scope of the destructive impact: 'this message will be sent to all users.' This complements rather than contradicts the annotation, giving the agent a concrete sense of the blast radius. No annotation contradiction.

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 sentences with no wasted words: action+audience, capability (bubble/carousel), and a deliberate warning. The warning in sentence three slightly echoes sentence one's 'all users,' but this repetition is justified emphasis for a destructive broadcast operation.

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 highly complex, destructive broadcast tool with no output schema, the description covers the core semantics and audience scope but misses operational realities: quota consumption (sibling get_message_quota hints this matters), non-reversibility of broadcasts, and any structural guidance for the message parameter. An agent would benefit from knowing this action cannot be undone.

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 0% for the single required 'message' parameter, so the description must compensate. It does add meaningful semantics by explaining the two layout options (bubble and carousel) that map to the contents oneOf in the schema. However, given the extreme complexity of the nested message object, it only scratches the surface—it doesn't mention required altText or the structural rules (e.g., body must be a Box).

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 specific verb (broadcast), resource (flex message), and scope (all users who added the LINE Official Account), making the tool's function unambiguous. It naturally distinguishes itself from siblings like push_flex_message (targeted) and broadcast_text_message (text-only) by naming the audience and message type.

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 makes the broadcast scope explicit with 'all users who have added your LINE Official Account' and reinforces it with the warning that the message goes to everyone. This clearly implies the push vs broadcast decision context, though it doesn't explicitly name alternatives like push_flex_message 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.

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

The annotation destructiveHint=true is reinforced and expanded by the description's explicit warning that the message goes to all followers, which is a significant behavioral consequence. This goes beyond the annotation by explaining the reach and potential impact. The description does not mention rate limits or response details, but for a broadcast action, the key behavior is covered. 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?

The description is two sentences with no filler. The main action is front-loaded ('Broadcast a simple text message via LINE to all users'), followed by a usage condition and a warning. Every sentence adds value, and the length is appropriate for the tool's simplicity.

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?

The description covers the core purpose, the usage condition (plain text), and the broadcast scope warning. It does not mention prerequisites like authentication, but that may be implicit for LINE API tools. It also lacks explicit mention of the alternative for targeted sends, but the 'all users' phrase covers that. Given the single nested parameter and lack of output schema, the description is mostly complete, with only minor gaps around explicit alternative routing.

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 schema description coverage is 0%, meaning the tool description must compensate for parameter meaning. The description only says 'simple text message' and 'plain text', but does not explain that the message parameter is an object with a required 'text' field and an optional 'type' constrained to 'text'. The schema itself does provide descriptions for the 'text' property, but the tool description adds no additional parameter-level guidance, leaving the agent to rely solely on the schema structure. This is a notable gap.

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 verb (broadcast), the resource (text message to all LINE followers), and the scope (all users who followed the Official Account). It also distinguishes from siblings by specifying 'plain text messages without formatting', which implies the existence of a flex alternative, and 'all users' which implies targeted sends. This makes the tool's purpose unambiguous and differentiates it from push_text_message and broadcast_flex_message.

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 explicitly says 'Use this for sending plain text messages without formatting', giving a clear condition for when to use it. It also warns 'Please be aware that this message will be sent to all users', which signals the impact and implicitly cautions against using it for targeted audiences. However, it does not name the alternative tools (e.g., push_text_message for targeted sends), so the guidance is helpful but not fully explicit about exclusions.

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?

The annotation already indicates destructiveHint: true. The description adds minimal behavioral context beyond 'cancel', not explaining consequences or reversibility.

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 extremely concise with no wasted words, appropriate for the simple action.

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 simplicity (no parameters, destructive annotation), the description is adequate but lacks explanation of what 'default' means or the impact, leaving some context 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?

With zero parameters, no further documentation is needed. The baseline for 0 params is 4, and the description does not add redundant info.

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 action ('cancel') and the resource ('default rich menu'). It is specific and distinct from sibling tools like set_rich_menu_default, though it does not explicitly differentiate when to use which.

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 guidance is provided on when to use this tool versus alternatives (e.g., set_rich_menu_default). The description lacks context about prerequisites or typical scenarios.

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 destructiveHint=true, so the description is consistent with that. It adds context about image generation and default registration, but it does not disclose side effects such as replacing an existing default rich menu or any limits. Given the annotation covers the mutating nature, the description adds some value but could be richer.

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 short (two sentences) and front-loaded with the main purpose. There is minor redundancy ('based on the given actions' and 'based on the given action') but it is not verbose. It earns a 4 for being efficient and readable.

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?

The tool is moderately complex (multiple action types) but the schema provides detailed structure. However, the description omits any return value or error behavior, and does not explain what happens to the previous default when this one is set. Given no output schema, the description should at least hint at the result. It is adequate but incomplete.

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% (both parameters have descriptions), so the description does not need to add parameter details. The tool description mentions 'actions' and 'image' but does not add meaning beyond the schema. Baseline 3 is appropriate since the schema carries the parameter documentation.

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 clear verb ('Create') and resource ('rich menu'), and adds that it generates/upload an image and registers it as default. This distinguishes it from siblings like delete_rich_menu, though it does not explicitly contrast with set_rich_menu_default. It is specific enough for an agent to know what the tool accomplishes.

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 no guidance on when to use this tool versus alternatives like set_rich_menu_default or delete_rich_menu. It does not mention conditions or exclusions, leaving the agent to infer from the 'registered as default' phrase. This is a significant gap for a mutating 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?

The destructiveHint annotation already signals that this operation is destructive, but the description adds little behavioral context beyond that. It does not state permanence, whether deleting a default rich menu has side effects, or any account-level implications.

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 a single, clear, active sentence with no filler or redundant content. It aligns closely with the tool's purpose and is immediately scannable.

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?

The description provides the essential operation and scope, but it does not mention side effects or special cases (e.g., deleting a default rich menu, irretrievability). Annotations cover the destructive nature, but the textual context remains thin.

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 only parameter, richMenuId, is fully described in the schema valence. The tool description does not add any detail about the expected format, where to find the ID, or how it is used beyond what the schema provides.

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 action ('Delete') and the resource ('a rich menu'), and it is scoped to the LINE account context. It unambiguously contrasts with sibling tools like create_rich_menu, get_rich_menu, or set_rich_menu_default.

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 no guidance on when to use this tool versus alternatives such as create_rich_menu or set_rich_menu_default. There is no mention of preconditions, when deletion should be avoided, or what happens if the rich menu is currently set as default.

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?

The annotations include readOnlyHint=true, which already indicates a safe read operation. The description goes further by explaining the purpose (obtaining IDs for messaging) and implying the data is a list, which aligns with the read-only nature. It does not contradict annotations, and the additional context about the use case enhances transparency beyond the annotation.

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 concise, with two sentences that directly state the tool's function and a key use case. It is front-loaded with the primary action ('Get a list of user IDs') and avoids unnecessary detail. Every word earns its place, making it easy for an agent to scan quickly.

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 simplicity of the tool (few params, no output schema, read-only), the description is nearly complete. The main missing piece is the return format, but with no output schema and the schema already providing param descriptions, this is a minor gap. The description sufficiently explains the tool's role in the context of messaging, which is enough for an agent to use 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 coverage is 100%, so the schema already documents both parameters (limit and start). The description does not add syntax or format details beyond that. However, it does implicitly convey that the result is a list of IDs and that 'start' is a continuation token, which is already in the schema. The description adds little incremental meaning, so a baseline 3 is appropriate.

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 function: retrieving user IDs of friends who added the LINE Official Account, with a specific purpose (sending messages). This distinguishes it from sibling tools like get_profile (which retrieves a single user's profile) and the messaging tools (which send messages). The verb 'get' plus the resource 'follower IDs' makes the purpose unambiguous.

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 implies usage for obtaining user IDs for messaging, but does not provide explicit when-to-use or when-not-to-use guidance, nor does it mention alternatives. Sibling tools like get_profile exist for retrieving individual profiles, but the description does not contrast them. The intended use case is clear enough for an agent to infer, but explicit routing is missing.

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. Description adds context about monthly message limit and current usage, which is valuable beyond the annotation.

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 sentences, clear and front-loaded with no extraneous 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?

The description fully covers the tool's purpose for a simple read-only operation with no parameters and no output schema.

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?

No parameters exist in the schema; description adds no parameter details, but baseline is 4 for 0-parameter tools with 100% schema coverage.

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 verb 'Get' and the resource 'message quota and consumption'. It distinguishes from sibling tools that are about sending messages or managing rich menus.

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 implies usage for checking quota before sending messages, but does not explicitly state when to use this tool over siblings or provide alternatives.

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, so the agent knows this is a safe read operation. The description adds the specific fields returned, which is useful context beyond the annotation. However, it does not disclose potential error conditions (e.g., invalid userId, user not found) or rate-limit behavior, which would be valuable for a read operation.

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 a single, concise sentence that front-loads the main purpose and lists the returned fields. It is efficient and easy to parse, though it could be slightly more structured by separating the purpose from the field list. No wasted words.

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 tool with one optional parameter and no output schema, the description is mostly complete. It covers what the tool does and what it returns. However, it lacks information about error handling, whether the userId must be a friend of the bot, and any authentication requirements, which are relevant for LINE API calls. The annotations cover the safety profile, but the description could be 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?

Schema description coverage is 100%, so the schema already documents the userId parameter. The description adds the default behavior (defaults to DESTINATION_USER_ID) which is already in the schema's default field. The description does not add significant meaning beyond the schema, so baseline 3 is appropriate.

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 purpose: retrieving detailed profile information for a LINE user, and enumerates the specific fields returned (display name, profile picture URL, status message, language). This is a specific verb+resource combination that distinguishes it from sibling tools like push_text_message or get_rich_menu_list.

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 implies usage for fetching a user's profile but does not explicitly state when to use this tool versus alternatives. It does not mention exclusions or prerequisites, such as whether the user must be a friend or have consented. The context is clear enough for a simple read operation, but no explicit when/when-not guidance is provided.

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 provide readOnlyHint=true, but the description adds no further behavioral context beyond that. It does not mention output format, pagination, rate limits, or any other traits. For a tool with no parameters and no output schema, the description should at least hint at the nature of the returned data.

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 a single, clear sentence with no unnecessary words. It efficiently conveys the tool's purpose without redundant 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 tool's simplicity (no parameters, no output schema), the description is minimally adequate but lacks details about the return value (e.g., whether it returns IDs or full rich menu objects), which would help the agent fully understand the tool's output.

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 and schema coverage is 100% (vacuously). According to the rubric, no parameters defaults to a baseline score of 4. The description does not need to add anything 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 clearly states the tool retrieves the list of rich menus for the user's LINE Official Account. It uses a specific verb (Get) and resource (rich menus), distinguishing it from sibling tools like create_rich_menu or delete_rich_menu.

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 implies the tool is for reading existing rich menus, but it does not explicitly guide the agent on when to use this tool versus alternatives. Since siblings include both read and write operations, some explicit usage guidance would be beneficial.

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?

The annotations include destructiveHint: true, which already signals that this operation has side effects. The description adds no extra behavioral context beyond the obvious fact that it sends a message. It does not mention any rate limits, authentication requirements, or other operational details, but the annotation covers the safety profile, so this is acceptable.

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 concise, using only two sentences to convey the core purpose and the two layout variants. It is front-loaded with the main action and target, and every word earns its place. There is no redundant or filler text.

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 extreme complexity of the message schema (nested objects, many options), the description is far too brief. It does not mention the required fields (altText, contents), the structure of the message, or any constraints. With no output schema and only 50% parameter coverage, an agent would struggle to construct a valid call without additional documentation.

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 only 50%, meaning the description must compensate for the missing parameter documentation. The description does not explain the message structure, the required fields, or the meaning of the parameters. The schema itself provides some descriptions (e.g., userId) but the message parameter is complex and undocumented. The description adds no value beyond what the schema already provides.

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 action (push) and the resource (flex message) and specifies the delivery target (to a user via LINE). It also mentions the two layout options (bubble and carousel), which adds specificity. However, it does not explicitly distinguish from sibling tools like broadcast_flex_message or push_text_message, though the singular 'user' implies a direct push rather than a broadcast.

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 provides no guidance on when to use this tool versus alternatives. It does not mention that this is for a single user vs. broadcast, nor does it reference the sibling tools or any selection criteria. An agent would have to infer usage from the name and context.

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?

The destructiveHint annotation signals that pushing a message has irreversible side effects, but the description adds no behavioral context such as immediate delivery, inability to recall, or quota implications. It repeats the obvious action rather than disclosing consequences.

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 by a usage condition. No filler or repetition.

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?

Adequate for a simple direct-message tool, but it leaves the destructive/side-effect nature unexplained and does not reference the broadcast/flex siblings even though the schema and annotations are otherwise thin. It is callable but not fully contextualized.

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 schema already documents that text is plain content and that userId defaults to DESTINATION_USER_ID; the description's 'simple text message without formatting' adds little. With only 50% schema description coverage and no extra parameter guidance in the description, the gap is not compensated.

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 specific action ('Push a simple text message to a user via LINE') and explicitly limits scope to plain text without formatting, which distinguishes it from sibling flex and broadcast tools. The resource, channel, and message type are all clear.

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 phrase 'Use this for sending plain text messages without formatting' gives clear conditions for use and implies it is not for rich content. It does not explicitly name alternative tools or state when not to use it, so it falls one step short of fully explicit 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?

The annotation destructiveHint=true is present, and the description aligns with that by implying a state-changing operation. The description does not add further detail about the irreversible nature or impact on other rich menus, but it does not contradict the annotation. Since the annotation already signals destructiveness, the description is adequate but not enhanced.

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 a single sentence with no extra wordslint. It is concise and to the point, achieving the goal without any fluff.

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?

The tool has a single parameter fully documented and no output schema, so the description's minimalism might suffice, but given the existence of related tools like cancel_rich_menu_default, some context on the effect on existing defaults or prerequisites would be helpful for an agent to understand the operational context. Thus, it falls short of 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?

Schema description coverage is 100%, so the parameter is fully documented in the schema. The description adds no additional meaning beyond the schema's description. Baseline 3 is appropriate since the schema carries the 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 states a clear verb and resource: 'Set a rich menu as the default rich menu.' However, it does not differentiate from siblings like 'cancel_rich_menu_default' or 'create_rich_menu', but the purpose is specific enough for an agent to understand the core function.

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?

There is no guidance on when to use this tool versus alternatives. For example, it could mention that this is used after creating a rich menu and that only one default can exist. The description provides no context for selection.

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