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

The annotations already declare readOnlyHint=false and destructiveHint=false, so the safety profile is covered. The description confirms this is an in-place field mutation and lists which fields change, but does not disclose whether omitted fields are left untouched (partial vs full update), whether the id must already exist, or permission requirements.

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?

A single sentence that front-loads the core mutation action and appends the disambiguation clauses. No wasted wording.

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 mutation tool with covering annotations, full schema coverage, and no output schema, the definition gives an agent enough to call it correctly. Remaining gaps are minor behavioral details (partial-update semantics, error/not-found behavior) that the annotations and schema do not supply either.

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 100% with self-documenting fields (id, text, alert, contextid, contexttype, notification), so the schema carries the parameter burden. The description adds only the grouped phrase 'context, notification flag or alert level', which adds no syntax or format detail beyond the schema. Baseline 3 is appropriate.

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?

States a specific verb (Change/Update), a resource (message), and enumerates the mutable fields (text, context, notification flag, alert level) plus the id key. It also names the two sibling tools this must not be confused with, so an agent can distinguish it from mark_message_read and snooze_message without reading 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?

Explicitly routes adjacent intents to alternatives: marking read goes to mark_message_read and temporary hiding goes to snooze_message. That is direct when-not/alternative guidance rather than implied usage.

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