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

With annotations only declaring destructive/idempotent/read-write hints, the description adds real substance: partial-update semantics, that a new schema does not retro-validate existing items but governs later writes and restores, that new rules take effect from the next write only after stored tests pass, that rules:null removes them, and that readonly blocks writes to the list, its items, and indexes. All of this is consistent with destructiveHint=true (notably schema and rules changes).

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?

Four dense sentences, front-loaded with the core semantics before the schema/rules/readonly caveats, and the trailing '1 request.' is a useful cost signal. It is cramped but nearly every clause carries 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?

An output schema exists, so return values need not be described. For a 14-parameter mutation tool the description covers the important behaviors an agent must know before calling: patching, schema scope, rules activation, and readonly. It stops short of stating what happens when the rules tests fail (error shape vs. silent rejection).

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 93%, so the schema already documents list, tags, rules, readonly, and the rest. The description's 'rules: null removes them' largely restates the schema's own null note, and its readonly note mirrors the schema wording. Baseline 3 is appropriate when the schema carries the parameter burden.

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 opening clause 'Change a list's fields; fields left out are left as they are' gives a specific verb, resource, and patch semantics, which cleanly separates it from update_item and update_index. It does not name a sibling alternative explicitly, so it stops 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?

Usage is implied rather than stated: the agent learns that rules require the stored tests to pass first and that readonly:true blocks writes, but there is no explicit 'use this when...' or 'prefer X instead' guidance across the 31 sibling tools. Conditioning behavior is present; routing advice is not.

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