[Bug]:Can agent skill fully take effect without explicit file-reading tool if only skill is registered?

## Description

I would like to clarify one behavior of agent skills in AgentScope.

According to the documentation, agent skills require text file reading or shell command tools so that the agent can access instructions inside `SKILL.md`.

However, in my testing:

* I only registered a skill using `register_agent_skill()`
* I did **not** register an explicit file-reading tool
* but the skill still appeared to take effect beyond just the metadata description

This makes me wonder whether:

1. skill can sometimes fully work even without an explicit file-reading tool,
2. some other registered tools may already provide enough capability for the model to access `SKILL.md`,
3. or whether the observed behavior is only due to prompt-level guidance from metadata.

## Minimal setup

```python
toolkit = Toolkit()
toolkit.register_agent_skill("my_skill")
```

In my case, there are other tools registered, but none is explicitly intended for file reading.

## Question

Is this expected behavior?

Has anyone observed similar cases where a skill seems to work even though no dedicated file-reading tool is provided?