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

Adds substantial context beyond the annotations: the token is the sole credential, a wrong token returns not_found identically to a missing plan (closing an enumeration oracle), and the payload deliberately excludes the other side's answer. That is strong auth and privacy disclosure. It never explains the annotations' readOnlyHint=false / idempotentHint=false, so any side effect of the call is left undocumented.

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?

Front-loaded with the audience and the security model, and the return contents follow immediately; almost every clause earns its place. Minor redundancy: 'NO IC ACCOUNT NEEDED' and 'No auth required' say the same thing, and the Args line duplicates the schema.

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?

With no output schema, the description correctly carries the return-value burden and does so well (specific fields returned and deliberately withheld), and it covers auth, errors and input shape. The only omission is any mention of side effects, which is notable given readOnlyHint=false.

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, but the description adds genuine meaning by framing token as the credential and describing its failure mode, plus identifying plan_id's origin (ic_plans_create / ic_plans_list). The 'Args: { plan_id, token }' line itself is redundant restatement of 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 states a clear verb+resource (read a plan as its invited guest, using the link token) and enumerates exactly what comes back: options, windows, your own answer, the current proposal and next_step. It implicitly separates itself from owner-side plan tools by insisting on the guest/token framing, but it never names the neighboring guest tools (ic_plans_guest_answer, ic_plans_guest_respond), so differentiation is inferential rather than explicit.

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?

It clearly scopes the caller: 'For the GUEST of a plan, or the guest's own AI assistant. NO IC ACCOUNT NEEDED' tells an unauthenticated agent that this is the right entry point, which is real usage context. It does not, however, say when to prefer it over the sibling guest_answer/guest_respond tools or what to do once the plan has been read.

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