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

With no annotations provided, the description carries the full burden. It clearly states this is a read operation ('Read'), and describes the kind of data returned (delivered, held, dropped). However, it does not disclose potential costs (e.g., large log sizes, performance implications), permission requirements, or any side effects. For a read-only log tool this is acceptable but not richly transparent.

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, immediately states the primary purpose and the key filtering options. It is front-loaded with the most important information and has no filler. Every word contributes to understanding the tool's function and usage.

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 that all parameters are optional, no output schema exists, and the tool is a simple read operation, the description covers the essential aspects: what the log contains, how to filter, and that it reads rather than mutates. It could mention the default number of records or clarify that 'last_n' controls volume, but the schema already includes defaults and descriptions, so this is not a critical omission.

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 provides 100% coverage for all three parameters (peer, last_n, thread), each with a description. The tool description reinforces these by mentioning 'Filter by peer' and 'follow a reply chain', which adds a little contextual meaning, especially for the thread parameter. But it doesn't add significant new semantics beyond what the schema already gives.

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 starts with a clear verb 'Read' and a specific resource 'Tin Can message log', and enumerates the core contents (what was sent, to whom, delivery status). It also highlights the two primary filtering modes (by peer or reply chain), which distinguishes it from the siblings 'peers' (listing peers) and 'send_peer' (sending messages) without confusion.

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 when to use it: to inspect message history, filter by peer, or trace a thread. It does not explicitly state 'use this instead of peers or send_peer', but the verb 'Read' and the focus on log contents make the context clear. It lacks explicit exclusions, but the purpose is unambiguous enough for an agent to route correctly.

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?

With no annotations, the description carries the full burden. It discloses that the listing is a live snapshot ('live', 'names change and sessions come and go') and enumerates the state values (idle | busy | unreachable), so an agent understands results may be stale after the call. It implies read-only behavior but doesn't explicitly state lack of side effects or error conditions, which keeps it a step below perfect.

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, each with a distinct job: purpose, return values, and usage timing. It front-loads the core action, uses a colon to attach the rationale, and contains no filler or redundancy.

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 parameterless list operation with no output schema and no annotations, the description is remarkably complete: it specifies what is returned, the meaning of state, and why to call it before send_peer. Nothing essential for calling it correctly 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 and an empty schema, so there is nothing to document. The baseline of 4 for 0 params applies. The description instead provides semantic value about return fields, which is helpful but not parameter-related.

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' with a specific resource ('live Claude Code sessions on this machine that you can message'), then enumerates the return payload fields and state values. This clearly differentiates the tool from siblings send_peer (sending to a peer) and message_log (reading message history).

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 last sentence explicitly instructs 'Call this before send_peer' and explains why: 'names change and sessions come and go.' This is direct, actionable guidance tied to the key sibling tool, with no ambiguity about when it should be invoked.

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?

With no annotations, the description carries the behavioral burden and does well: it discloses fire-and-forget semantics, when the function returns, and the peer's independent-agent limitation. This is meaningful behavioral context beyond a simple 'send' description. The only minor gap is unspecified error/return details, which are peripheral for a fire-and-forget call.

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, each earning its place: first states the operation, second defines the async behavior, third gives naming guidance and the peer limitation. There is no filler, redundancy, or restatement 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 5-parameter tool with no output schema and no annotations, this definition is nearly complete. The description explains return timingarena, the schema documents all parameters, and the naming guidance ties to the sibling peers tool. The one missing piece is what the return payload contains (e.g., a message id for in_reply_to), but the fire-and-forget framing makes this low-risk.

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 baseline is 3. The description adds value by explaining that peer names come from the peers tool and that an unambiguous prefix is accepted, which is more actionable than the schema's examples. It also reinforces that the message is sent verbatim, aligning with 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 opens with a precise verb and resource: 'Send a text message to a live Claude Code session on this machine.' It is immediately distinct from the sibling peers and message_log tools, which list peers and read logs rather than send. The fire-and-forget clarification further pins down the tool's purpose.

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 practical usage context: 'Use the name from peers; an unambiguous prefix works' tells the agent how to construct the peer parameternail. It also states an important exclusion — 'The peer is another agent with its own human — it cannot approve anything for you' — guiding when not to use this tool for approvals. It does not explicitly mention sibling tools as alternatives, but the usage context is clear.

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