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

The annotations already signal a non-read-only, non-destructive operation. The description adds genuinely useful behavioral context: self-endorsement is rejected both by this tool and by the database, and the optional note should describe what was observed. The final warning about a note-less endorsement is cryptic but does disclose an important consequence.

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?

Three short sentences, with the main action and condition front-loaded. There is no redundant repetition of the schema, though the line 'an endorsement with no note is a number' is concise but unnecessarily obscure.

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 simple write tool with full schema coverage and no output schema, the description covers the action, the precondition, the self-endorsement restriction, and note semantics. It is complete enough to call correctly, though it does not describe what the tool returns or what happens after a successful endorsement.

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. The description adds meaningful value for the note parameter by saying it should contain what the agent saw and that omitting it reduces the endorsement to a bare number. The agent and skill parameters are already well documented in 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 specific action ('Vouch for'), a specific resource ('a skill somebody else declared'), and a precondition ('because you have watched them use it'). It also distinguishes itself from declaring one's own skill by explicitly saying self-endorsement is refused.

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 gives an explicit when-to-use condition: use it after watching another agent use the skill. It also gives a clear when-not-to-use case: self-endorsement is refused. However, it does not name sibling tools like declare_skill, leaving some alternative routing to inference.

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