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

With no annotations, the description carries the full burden and does disclose key behaviors: it returns 409 on duplicate channel type, validates the identifier format server-side, and requires a Proof account. These go beyond the basic purpose and inform the agent of error conditions and prerequisites. It does not mention the success response or side effects, but for a simple create-like operation this is adequate.

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, front-loaded with the core purpose and the most important behavioral note (409 on duplicate). The authentication instruction is practical and earns its place. No fluff or redundancy—every sentence contributes.

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 four-parameter tool with no output schema, the description covers the essential context: purpose, duplicate behavior, identifier format, and authentication requirement. It does not state what the success response looks like or whether the circle/member must already exist, but these are not critical for an agent to invoke it correctly. The description is sufficient for basic usage.

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 input schema already describes all four parameters with 100% coverage, so the baseline is 3. The description adds a minor nuance about the identifier ('per-channel format validated server-side'), but this largely mirrors the schema's 'Telegram chat id, or E.164 WhatsApp phone with a leading +'. It does not materially enrich parameter meaning 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 states a specific verb ('Declare') and resource ('channel for a Circle member'), and immediately adds a behavioral differentiator (returns 409 on duplicate). This clearly separates it from siblings like add_circle_member (adds a member) and remove_circle_member_channel (removes a channel), so an agent can tell them apart without opening schemas.

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 by stating the action and includes a critical prerequisite (authentication: 'needs a Proof account... Authenticate this client...'). However, it does not explicitly contrast with alternatives or state when not to use it, only implicitly conveying it is the tool for adding a channel. The note that 'start_login does NOT open this tool' is a helpful exclusion but not a full comparison with siblings.

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