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

Annotations already signal that this is a mutating but non-destructive operation (readOnlyHint=false, destructiveHint=false). The description adds useful behavioral context: the presence or absence of member selects add-vs-update, and unregistered users are outside this tool's scope. It does not list all side effects, but the schema covers permission-list replacement, so the added context is sufficient.

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 compact: three short sentences, with the core mode distinction first and the relevant alternative routed at the end. Every sentence earns its place and there is no filler or repetition of the title.

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 two-mode mutation tool with 7 parameters and no required fields, the description resolves the main ambiguity (add vs modify vs invite) clearly. The exhaustive schema fills in parameter-level details. A minor gap is that it does not explicitly state which parameters become required in each mode or describe the return value, but an agent can infer this from the description plus 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?

Schema coverage is 100%: every parameter has a meaningful Russian description, so the baseline is 3. The tool description reinforces the member/email mode split and the role-override behavior, but it does not add much beyond what the schema already states for each parameter.

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 names a specific operation with two clear modes: adding a registered user by email when member is absent, and changing a member's role and granular permissions when member is present. It also distinguishes itself from invites_create, which is for unregistered people. This makes its purpose unmistakable relative to siblings like members_list and members_remove.

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 states when to use this tool (add an already-registered person or modify their rights) and when not to use it (unregistered person: create an invite via invites_create). This direct routing to the alternative is exactly what an agent needs to select correctly.

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