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

Annotations already declare destructiveHint=true and idempotentHint=false, and the description adds useful operational context: providers may only guarantee message uniqueness inside a chat, and certain values must never be passed. It does not describe effects like what happens if the reaction is absent, but the annotation safety profile lowers the burden.

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 verbose and repetitive: the Chat ID and Message ID blocks follow the same 'Obtain with... Never pass...' pattern and are duplicated verbatim in the schema parameter descriptions. The opening sentence is clear, but the overall length is disproportionate to the tool's simple purpose.

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?

Given no output schema, the description covers the critical knowledge an agent needs: how to resolve and pair chat_id/message_id, provider-specific caveats, and explicit negative examples. The account_id disambiguation lives in the schema and is well handled there. Minor gaps like the effect of removing a non-existent reaction are negligible.

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%, so the baseline is 3. The main description mostly duplicates the schema text for chat_id and message_id rather than adding new meaning; reaction and account_id are only documented in the schema. No significant parameter clarification is added beyond what the schema already 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 first sentence states a specific verb, resource, and scope: 'Remove the user's reaction from one exact message.' This cleanly differentiates it from siblings like message_add_reaction, message_list_reactions, and social_remove_post_reaction. No ambiguity about what the tool does.

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 gives explicit resolution steps ('Resolve chat/message first') and precise provenance for IDs ('Obtain with: provider list conversations/inbox chats -> chat.id'). It does not explicitly name alternatives or state when-not-to-use, but the context is strong enough for an agent to apply it correctly.

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